Not bad when looked at as on it's own and not compared to the PC game.
That being said Battlefield 2: Modern Combat has unfairly been reviewed by many in the shadow of the incredible PC game. I'm building a new PC and will be playing the hell out of Battlefield 2 in a month or so. Until then I thought I'd give BF2:MC a try on my Xbox. I'm not sorry I did as I have been enjoying it quite a bit.
There is a single-player game and it is an improvement over playing the bots in BF1942, so is watching paint dry so that's not saying a whole lot. If you do not have Xbox live then there are other tactical shooters on the Xbox that are much better. The single-player campaign isn't awful but it isn't great either. The hotswapping function is very cool, I think we'll be seeing this a lot in future titles. The AI however is pretty bad, your troops tend to stand around not doing much.
Multiplayer is what the BF games are all about and while this is not the PC BF2 it is still a fun game. One of the biggest disappointments I've had with Xbox live is the idiotic behavior of many players. It seems that many console gamers have never learned the concept of teamwork, no matter what the game they run around like morons killing teammates and themselves. Maybe this game just attracts brighter people than Halo2 (or less kids though I've played this game with some young sounding people who were good team-players).
The weapon load-outs and vehicles are fairly evenly balanced and the maps are good sized for the smaller teams console gaming makes necessary.
Like pretty much every EA title this year the game manual is absolutely PATHETIC. There is a lot to learn with this game but EA couldn't be bothered to even put the complete game controls in the manual. Luckily I've met some patient players who helped me learn the ins-and-outs of the controls and maps. Be patient and don't let the fools who think that having lots of spare time to get good at a game means that they are better people than new players ruin it for you.
Modern Combat is definitely not going to win game-of-the-year awards but it IS a fun tactical shooter. It's worth checking out if you don't yet have a PC capable of running BF2.