The original Voodoo cards were absolutely incredible... the first video card I used was a Voodoo Banshee on Dark Forces II: Jedi Knight. I was absolutely amazed at the 3D graphics (first time I had seem them on an actual computer). And, the game actually ran faster on the 3D settings because it was utilizing the GPU's power.
The Radeon 9700 Pro was revolutionary. I don't think anyone will argue that point. Its release in Q3 2002 shocked the public by a bandwidth of almost 20 GB/s, compared to other high end cards which couldn't do half that. It was the first card to really support DX9, which would come to be the standard of games for years to come (and still is for the most part). And believe it or not, this was the first card to actually support HDR as well (source).
I voted for the 9700 Pro, but both of these cards revolutionized the computer gaming experience IMO.