Just last week I would have said CoD4, as I would have assumed the online community would be superiour to CoD5 just due to how many people own the game, but since CoD5 is selling so well, I suppose that's no longer an issue.
I have not played CoD5 yet, so I don't know anything about the quality of it, but CoD4 is a fine game. I think you would be happy with either one, so you should probably decide whether you want to play with modern weapons or WWII guns and choose accordingly.
As far as other game recommendations, if you have Live, definitely pick up Left 4 Dead. I've had more fun with that game than almost any other I've played this year. Dead Rising, Orange Box, Viva Pinata, and Fallout 3 are also pretty much guaranteed to be enjoyed.
Depending on your tastes, you might like Tales of Vesperia and Lost Odyssey, too.
LEFT 4 DEAD - November 17th
