have a buddy who swears by NVIDIA cards, as that's all he's used for over 5 years. he's tried many cards and has singled it down to the NVIDIAs because all he does is play games.
i upgraded from an older NVIDIA to a GeForce2 about 6 months ago (free card!) and was amazed at the difference. nice, IMO.
They have long since fixed that problem. ATI has been steadily pulling ahead of Nvidia. Depending on which benchmark you use, ATI wins a lot of them. Never go by Tom's hardware as he is biased and crooked as hell
I'm partial to Nvidia solely because of their APIs - and I rarely even program for graphics shit, so I don't know why I even care.
I've had both in my systems, but now I am on laptops nearly all the time (at least at home), so it is largely a moot point.
I don't even know what is in this thing that I am on now.