Team Fortress 2 at first glance may seem to be an average first-person shooter game- interesting but not outstanding. Upon closer inspection, however, you'll probably find that it's better than average.
Though not as popular as some other mainstream first-person shooters, such as Call of Duty: Modern Warfare 2, it's actually much better value for your money. Though the game was released nearly three years ago, it is continually updated and still has a large player base. Though most games would be blessed for free bug fixes three years after a game is released, this game is updated with free massive updates, nearly doubling the original size of the game. Even without these updates, the game would still be incredibly good. With nine different "classes" to play as, all of whom are incredibly different, the game is quite balanced. You can choose between less durable, quicker classes, interesting classes with unorthodox weapons, such as the Demoman, who lays traps with various bombs, or powerful, hard-to-kill classes who can easily be killed by a long-range shot from a Sniper.
The gameplay is very enjoyable, with a lot of different things to do. The atmosphere of the game is friendly, with each class having a distinct personality, and great voice acting. However, there's a steep learning curve, and it can take a while to learn the ropes. All in all, it's a very good game that's worth buying.