In Splinter Cell you miss the highest quality shadows with ATi parts which are there even on the NV2X boards from nVidia. This isn't due to SplinterCell being aimed at nVidia graphics cards, it is due to the fact that the game was XBox native. The effect they use in SC for the highest quality shadows isn't directly supported by DirectX, although obviously it is possible using the API. Other then that I can't think of any other instance where nV is rendering any effect ATi isn't(there was a problem with NeverWinterNights and some shader effects some time ago, but that was fixed with a patch).