Quite frankly, the answer is no. It's more of a rental game or a game you should get when it's severely discounted ($30 persay, instead of the full $60). Although Bungie DOES market it as a full on game to the Halo series, it plays a lot more like a simple expansion pack due to the extremely short campaign and simplicity of Firefight. The hype about this game may have caused it to lose some of it's luster once played. But let's not make this a biased review and look at the cold hard facts.
Halo. An extremely profitable franchise on the Xbox open to hardcore and newbie players, the story sucks you in, and the gameplay and competition keeps most people going. Bungie (and Microsoft) fully aware of this fact, decided that since you've played through the Master Chief's version of events throughout the series thus far, it's time for a different perspective. In comes the ODSTs (Orbital Drop Shock Trooper) who, if you follow the series closely, are elite soldiers in the UNSC (United Nations Space Command) who are also sent into battles that are severely one-sided. However, unlike Spartans who were trained from birth to be soldiers and can severely adapt to almost any situation with their suits of apparently indestructible armor, these soldiers are just soldiers that were originally in the Marines and wanted more kick to their jobs. They are similar to the Navy Seals, Delta Force, or the SAS in their respective military branches. Their motto: "Dropping into hell feet first" is taken quite literally because they drop from low planetary orbit in single man drop pods that reach crazy high temperatures during transit, and can land anywhere in the heat of battle. They wear black armor with full on helmets similar to the Spartans, however, they do not have the shields that the Spartans do, which causes for a different style of gameplay (we'll get into that later).
The ODST you play as is named "The Rookie" because he is new to the squad (but not inexperienced or "green" persay to fighting) and because he never talks in the game. At all. And he's sorta like the Chief in that he never ever takes off his helmet either. Anyways, you meet your new squad and get dropped straight into battle, which leads to this awesome cinematic-like sequence where you are strapped into the pod and can free-look at space and whatever stuff you happen to be dropping past in your pod, very cool. However, as you teammates' and your pod drops closer to the landing zone (on Earth) a Covenant ship in orbit has decided that it had enough of getting it's ass whooped and decides to leave, ripping a hole in space to reach light speed. Unfortunately, this causes EMP damage to everyone's pods and the landing goes horribly awry. As the Rookie, you crash into a building and promptly get knocked out. Waking up 6 hours later, he finds that he is alone in the cityand goes off in an epic search for his "missing" teammates.
Now here is where it gets super freaky. As you move through the city (which is enemy infested), you find "clues" that your teammates left behind, like a security camera or a helmet somewhere (I won't give away all of them but these are some of the clues you find). I swear to God, the Rookie is the reincarnated futuristic version of MacGuyver. He finds these miniscule clues and deduces exactly what happens when and where in his mind's eye. Now in the game, every time you find a clue it jumps to the perspective of one of your teammates and play as them for a while (apparently they weren't knocked out by their crash landings) until it explains the clue you found. Then you switch back to the Rookie, who with his super powers of logic and crazy ass smarts, proceeds to accept what he believes to have happened and continue on his way in the dark to find more clues and hopefully his teammates. What the hell. Smart ass bastard XD. However, he seems to be too smart for his own good because he manages to solve everything that happens after about 4 clues and (ahhh screw it, it's a review *MINOR SPOLIERS*) meets up with his squad, which is why I said the game feels like an expansion and not a full game.
But there are those who cry out "It's a Halo game! Plays exactly the same!", and well, they can just shut the hell up. It plays somewhat more like Call of duty 4 now because instead of shields, you have stamina, which turns your screen red when you are hurt badly, and then if you run out of stamina, you start losing health (yeah the health bar makes a comeback, so the medpacks actually do something now). To recharge your stamina, you take cover and slowly your screen turns back to normal colors. This mechanic is important in that you can't rush headlong into battle anymore and expect to survive (unless you're crazy awesome like some players out there); you have to pick and choose when and what to battle. You can choose to let enemies walk by (going silent), kill some of them, or just completely decimate squads (going loud). And with several of the new weapons (Halo 2 Pistol with a scope, Silenced scoped SMG, increased grenade capacity, etc) it's completely possible to do so. In the original Halo series, it was mostly spray bullets at enemy, watch them implode into tiny bits; in ODST, headshots allow you to dispatch enemies crazy fast and is what you should be aiming for in every encounter that you come across. All in all, your gameplay style will be assuredly different (unless you're insane at FPS games) and will probably focus more on a steathy factor.
Now ever since...I want to say Gears of War 2, but something may have been earlier than that. Ever since GOW2's Horde mode did surprisingly well, game developers have started to look into building "Horde like modes" for their games, because apparently kicking ass with 3 other friends against wave after wave of enemies is fun (and it is). Treyarch made Nazi Zombies (which I believe should have been it's own flipping game instead of just being a part of the fail that is COD:WaW) and so Bungie made Firefight. Now what sets Firefight apart from other horde mode games is that it implements the Halo universe, most importantly the skulls from Halo 2 and Halo 3 that made the game considerably harder. As the AI throws more and more enemies at you, skulls turn on and off in order to make things more complicated for you and your teammates. Skulls have different attributes like making the enemies stronger against human weapons or making it so that your stamina only recharges when you melee an enemy (med kits recharge your health and stamina, so use the sparingly). Here's where the explanation gets complicated, so try to follow along as best as you can. Ok here we go: Each set has 3 rounds which consists of 5 waves each. At the start of every round within a set, a skull in a predetermined group of three (Tough Luck, Catch, and Black Eye) gets turned on and stays on for the rest of the set. The same goes for the start of every set, except with a different set of skulls (Tilt, Famine, and Mythic). So if you progress far enough into a match, eventually every skull will be turned on and you will be hard pressed to survive. For those of you who don't really get what I meant back there, let me give you an example: Let's say you progress to Set 2, Round 2, Wave 3. Since it's Set 2, one of the skulls from group consisting of Tilt, Famine, or Mythic will be turned on (none of them are turned on during the very first set cause then it'd be kinda hard lol) and since its round 2 within set 2, two of the skulls from the group consisting of Tough Luck, Catch, and Black Eye will be turned on. When you reach round 3 of set 2, all the skulls from the "Round skulls" will be on, but the skull in the "Set skulls" that was previously on before will still be the only one on. It doesn't change until you reach the next set (remember each set has 3 rounds that consist of 5 waves each).
If you thought that was complicated, well then the good thing is that it gets less complicated to understand the rest of Firefight. You and your teammates have a set number of "pooled" lives, meaning that if someone in your group dies, EVERYONE'S lives number goes down by one, not just theirs. This means you have to work together to survive, and can't just go rambo everywhere like you did in Halo 3. The good thing is that you have the opportunity to gain a predetermined (man I'm using this term a lot) set of lives at the end of every round depending on how many players are playing and the map you play on, and another chance to gain extra lives at the end of every set (basically all the skulls including an extra one that stops people from respawning are turned on, a ton of easy to kill enemies are placed on the map with heavy weapons and you have to reach a specific score and survive a minute in order to receive the extra lives. If noone survives, no lives are added or taken away). The enemies spawn via Phantoms (enemy air transport vehicles) that land in several predetermined locations depending on the map you play on and you can just spawn kill them as they come in, though the ship might take several "potshots" at you (and trust me, a ship taking "potshots" at you isn't a good thing, so it's not advisable to be in the open while the ships are around). Pistols and SMGs always spawn on map no matter which one you're on, but several "heavy weapons" are given to you on different maps, like on Windward you spawn with sniper rifles and on ONI Alpha Site, a rocket launcher spawns on the map. Use these weapons wisely, because you don't get another chance to get them until the end of every round. So yeah, ammo conservation is a must in this mode.
Problems and complaints with this game:
For me, the story was totally awesome but crazy short. Bungie had a lot of potential with this game but instead they rushed it and came out with a halfway decent campaign. For experienced Halo players, it takes about 2 hours MAX to finish the campaign on Legendary. It's that easy. I guess Bungie was relying mainly on firefight in order to counter balance the failed campaign. And it does to a "WTF?" extent. If you play Firefight with halfway decent people, the average game (how long you guys will last without running out of lives) will last you seeral hours. That right, HOURS not minutes. ONE match. Just one. It takes a while to run through all of the skulls and to kill the specific amount of enemies before the AI realizes that you just raped a wave and proceeds to send more retarded enemies your way so be prepared to sit on your ass for a while: get some food and stock up on drinks. Let me give you an example: I don't have that much time to play games anymore so my Halo skills have considerably degraded. I played a game of firefight alone, by myself and managed to make it to Set 5, Round 2, and wave 3 before finally deciding to take a break and repeatedly killed myself to end the game and get the stats. I could have easily kept going past where I stopped but chose not to because I had already been playing for about 4 hours straight.Yeah....so Firefight. Not for the weak-hearted.
All in all, the game is a fun one, but you shouldn't get it for full price due to the imbalanced play times. Firefight takes forever, the capaign lacks so much promise, and it plays like a $20 XBL Marketplace expansion (which is what it was originally meant to be, but they figured "Hey, let's tack on a Horde mode and call it a new game"...ugh). If you can get it for cheap, I'd suggest doing so, but otherwise just borrow it from someone else.