Ace Combat 6 is not a must-have game. It's not a system seller, and it probably won't win game of the year. That said, this is a great game and easily the best flight sim/arcade games ever to appear on any console.
Ace Combat 6 is the first game in the series to make the leap to a next-gen console, specifically the Xbox360. The results are simply stunning. The graphics are clean, detailed, and never hiccup despite the hundreds of planes, tanks, and ships on screen at any given point. Hollywood movies don't look this good. The sound is equally strong. The soundtrack is good (meaning basically non-intrusive), but what really stands out are the sound effects. One of the best moments in gaming is flying through the debris of another aircraft and hearing bits of metal bouncing off the cockpit of your aircraft.
Considering the obvious time and care put into the presentation of Ace Combat 6, it wouldn't be surprising if the the gameplay suffered. Fortunately this is not the case, as Namco has struck just the right balance of arcade and simulation type control. You won't be doing any fancy reverse stall-outs, but the physics are solid and basic dogfight maneuvers work well. It's easy to pick up and play, but dedicated gamer will find a lot of depth.
The major weak-point of this title is the Campaign mode, which is a great time while it lasts. Unfortunately that's only about 5-6 hours for the average player. The numerous achievements and bonus content really help the replay factor, but the main story could stand to be about 25% longer. In the same vein, the online options are fun, but there really aren't enough unique maps to keep you interested. No doubt we'll be offered more (for a price) on Xbox Live in the near future.
All in all, a great game for everyone, and a must-have for fans of the series.