I suggest PCLinuxOS as a good distro of Linux, very stable and very customizable. As far as gaming goes though, Linux runs into a lot of snags though it can be done. Doom3 is actually Linux-friendly from what I remember (don't play the game myself) and with the help of Cedega (
http://www.transgaming.com/products/cedega/) you can run even more. The only downside to that is Cedega requires a monthly fee, kinda defeating the point of Linux. I dual boot to avoid this problem, using XP for gaming only and PCLOS for schoolwork and just general web browsing.