How big is the monitor you are driving? If it is a 22" at 1680x1050 then a GTX 470 can top the settings on any game.
At 1920x1080 you won't be able to max all settings in game but would get you really really far if you just turned down AA. The more demanding games like Crysis would make your card struggle even if you turned down AA but nobody needs that kind of performance.
A GTX 470 would definitely be the better buy IMO
Im running crysis at 1920*1080 at average 34fps, very playable, little noticeable lag, with a GTS 250... and that thing deserves a place in a museum