I don't know about the best, but the most fun I've had with a FPS is Killzone on the PS2. It was a little glichy, but good, gritty graphics, pretty decnt story for a console FPS, love the weps were standardish, but still fun. If I could have any wep from the game it would be th Helgaust assalt rifle.
But one of the most impressive parts of the game was the voice acting. Unbelivably good.