I think forums are much better than review sites anymore. I want a good game, not another Quake clone or some retro sequal that never lives up to the orginal. I don't care if it's FPS, RPG, RTS, etc., just good. If a game is generating a ton of forum posts, with screen shots, and discussion about game-play elements then you can guage whether it's worth trying.
It's not 100% accurate though. I was suckered by DoomIII. The forums were all lit up and it took about a week for the whole monster closet crap to come out... and still people liked it. I generally stay away from the twitch shooters since I like more refined team based multiplayer, but that's just me.