The 5950 would do fine with any current game, most people are just biased towards PC hardware. You can get what you want, but you will get the best performance from ATI 95% of the time, though most of the time it's by a small margin.
The biggest difference you will see is maybe a few FPS in games that they benchmark the cards with. Although, you WILL be able to overclock a bit more with Nvidia cards, but you shouldn't have to worry about overclocking any of the current "high performance" cards for a while.
So the X800 will give you the best performance, second to that is the 9800 XT, then the 5950, and even a 9800 Pro or 9700 Pro is still more than enough for current games.