Halo rocked. Best FPS (next to Deus Ex).
I ignored the hype, the bitching (anti-hype?), and saw it and played it for the first time on the PC. I thought the game was a lot of fun. Referring to Halo btw.
As for best FPS however. Deus Ex was pretty fun (the MP patch being much fun), but the Best FPS? I think not.
My favorite FPS's over the years have been System Shock 1/2 and Tron 2.0. Note the similarity between those three : )
Is one of those the best ever? For me, yes, but being the best, just like everything else talked about on this/any forum is subjective : )