Call me retarded, but from past experience Halo is always way more fun splitscreen than Call of Duty.

My friends used to come around to my house a lot to play splitscreen, and Call of Duty never quite satisfied our needs.
Later I discovered that Call of Duty is really only fun when there are lots of people in the game, 4 just doesn't work. It's the kind of game where you go in, run around and shoot anything that moves.
Halo on the other hand is slower and more "tactical" shall I say, something about it just works way better for splitscreen.

But for online play in my honest opinion Call of Duty was always way better. Feel free to disagree with MW2's brokenness, I still really like it. As of late the only shooter I've been playing is CoD4.

I love how everyone seems to have forgotten about Medal of Honor.

Well yeah singleplayer's all fine and dandy but at the end of the day the only reason we're getting either game is for multiplayer, which we'll be playing for years and years to come(until CoD's next 5000 sequels).

Though in terms of singleplayer yeah I'd agree, Call of Duty wins, no question. It's so fast paced and all, feels like a summer blockbuster movie and stuff. Halo, I dunno just doesn't seem to click with me gameplay wise. Story is good but I dunno the missions feel way too meh OH GO FROM POINT A TO POINT B SHOOT SOME THINGS etc.

You should try Halo MP imo, even if you don't entirely like the SP campaign there definitely is some appeal to it.
Weapons are a lot of fun and lots of sploddy things and stuff, give it a shot.