Well, according to MaximumPC, December, 2007 issue, pp. 22-42, and in considering the 100 greatest PC Innovations of all time, the 3dFX Voodoo1 was ranked #2 (1996), the #1 ranking going to the ubiquitous USB port (1996). Other video cards listed were the nVida Geforce2 # 16 (2000), IBM CGA card #24 (1981), Matrox G400 Dual Head #31 (1999), ATI Radeo 9700 #48 (2002). I'm not sure I could agree with all of their selections, but definitely, the Voodoo series stood in a class by itself.
Having owned most of the cards listed in this thread, I'd have to go for a tie for #1, Voodoo1 & Voodoo 2 (which were absolutely earth-shattering at the time), the original GeForce with DDR memory tied with the 8800 GeForce series at #2, followed by the ATI 9700 Pro. All of these cards lifted the bar considerable over the previous generation of cards - none as much as the Voodoo.
Just my 2 cents...