The more the merrier. Its just going to be chaos when all the graphical comparisons or exclusive DLC/add ons start being shown/announced. Plus when all the sales numbers come in it'll ignite some emotions from fanboys. I bet Sony will give some kind of impetus to by the PS3 version over the 360, heck, Microsoft might offer something of their own too.
I don't think that it needs it, but if it's well done it will be a welcomed addition. I bet it will resemble Gears very much so, which might be nice because I've nevered played Gears and I hear it's fun.
Killzone 2's AI is the best I have seen, strategy wise, balance wise. I think some games are garbage when they make the AI in a shooter have a perfect shot. Unreal Tournament 3 is bogus on normal difficulty, the AI can shoot across the map with insane accuracy where in any normal AI situation you would be out of their immediate range, it lacks a AI point of view.
No, it's a pretty unappealling game. Jack Black is funny, but has obnoxiously annoying singing voice, with his BLEEDLE BLEEP BLEEDLE BLOOP BLEEDLE BLAPs and what not. I got my money on this game sucking.