What have I missed/Should I build a new pc

I currently have an old Athlon 2600+ system that I built about six years ago as well as an Xbox 360. The last games I bought for the pc were Doom III (barely playable) and Civ IV. I really haven't even looked at pc games for a couple of years. While I enjoy playing on the console, I miss playing on the pc (also my old cabinet lcd projection tv has glare issues, so gaming during the day is pretty much out). I generally play single player games and enjoy your basic rpg/dungeon crawler, fps type games. I'll probably get Fallout 3 for the Xbox when it comes out. I'm really, really looking forward to Diablo III but it is a ways off. I've gone through Dungon Siege II, Sacred, Titan Quest and Oblivion, Half Life 2, Farcry (it's been a while) on the pc. I've got Mass Effect, Bioshock, COD IV, GTA IV on the Xbox.

So, the question is, what good RPG,FPS single player games for the pc have I missed in the last year or so/coming out soon? I'm kind of thinking I might just wait until next summer to build a new pc, but am also kind of excited about building one now, and catching up on some games I've missed (if I can find them cheap at Fry's, even the better). I don't mind throwing some $$$ towards a new pc now, but if I haven't really missed much, the Xbox is always there and I can wait for Nehalem to be released and prices to come down before Diablo III.

Depending on the software situation, I'd rather not spend money now on a new pc, when I can wait a while, buy games for the 360 and build a better system a year from now when Diablo III comes out.

Thanks in Advance