For FPS I've got to say overall the best single player has been COD4 this generation. That is... minute for minute. It's not that long but it's very enjoyable, which is what matters most for a FPS. Resistance is up there though, it's not nearly as pretty looking, nor does it feel nearly as real. Like people say, it's the Halo of the PS3, but they feel very different in action. When I play Halo I feel very out of sync with my character. I mean, the controls are tight, and everything, but I don't feel like a guy on the ground with a gun, I feel like I'm controlling the character on strings like a puppet... cause he doesn't move like people really move. On a technical level, Halo is the better game. It's got the better options, and the better online despite being peer to peer.
There's no real lag anyway. The 40 man deathmatches aren't all that needed, the numbers only help on games like Warhawk. Resistance just makes me feel like I am the character I'm playing though.
They're both head and shoulders over The Darkness, Jericho or whatever else has been churned out over this generation though, even though they both have their imperfections. Call of Duty 4 is the best of both of them, to me. I feel like I AM the character, like Resistance, and it's got the great balance, speed and refinement of Halo. The only thing is Halo you can play online splitscreen, which means when other people are over, that's the best online FPS. But if there are other people, Warhawk is the king, no questions asked. Being able to jump in and out of matches mid game, the screen splitting without a single interruption is just too good.
Pretty much anything I haven't mentioned isn't worth mentioning except Rainbow 6 is awesome and they just announced a 2nd which is great.