ditch cs and just say CS:S.
Generals is pants... EA butchered a wonderful game in C&C.
Neotokyo was AWESOME! More neotokyo! I was surprised how well it played, i'm not a UT2K/Quake fan but neo was more my kind game. Obviously you need air bucaneers too.
Civ4 would be cool however there is two problems with it 1) it takes ages! 2) even with the latest patch its not 100% stable and its not fun when you crash out of a 4 hour game just as you're about to win.
Rome Total War would be cool and DoW Winter Assault would be even cooler... Winter Assault is a massive improvement in gameplay over standard DoW, get it if you don't have it already.
BF2 is cool but demanding, however most ppl seemed able to play it with the gfx turned to uber-blocky and it was fun! Sam if you need a gfx card i'll let you borrow my old FX5600 - it managed BF2, not great but good enough.