My 8800gt could do Crysis decently (would chug in moments of lots of action) at the highest graphical settings possible (though the resolution wasn't that high and the AA was either at 2x or off) and that includes the config trick to enable the unavailable settings on XP.
I don't know a whole lot of performance benchmarks though nor do I know the selection of ATI cards available (to get both sides of the spectrum mentioned). I recall the Radeon 4850 having some better performance than the 8800gt's for a similar price last year.







