Bad Company / COD4 (Modern Combat)
COD5 (if you like WW2)
Forza2 / Race Pro (Racing)
高達無雙2 / 三國無雙5 / 戰國無雙2 / 無雙orchi 2 (無雙series)
Virtual Fighter 5 / Soul Calibur 4 (3D格鬥)
SF4 (2D格鬥)
FIFA09 / WINNING 09 (足球game)
NBA2k9 / NBA Live 09 (basket ball game)
Devil May Cry 4 / 忍龍2 (action game)
GOW2 / Lost Plannet Colonies (TPS)
Left 4 Dead (Co-op action + shooting game)
Infinite Undiscovery / TOV / Star Ocean 4 / Last Remnant (日式rpg)
Fable 2 (美式rpg)
Halo Wars (SLG)

I only got Battle Field: Bad Company (BF:BC), so can't compare COD4 for you. But I think both of them are good and I like BF:BC more since I played most of the BF series.

For COD5, it is a FPS with WW2 theme, it sounds ok to me because I like Battle Field which was also a WW2 FPS at the first beginning. But most people here prefer COD4 because modern weapons and armors seems more attractive.