Ah, so it's the visuality that your worried about. But it's not that bad. I mean, there are some great games that have alot of split screen in them.
Imagine the best single player game you can, and then picture your friend playing at the same time, helping you, or controlling the enemies(million dollar idea).
I'm thinking mostly of Zelda here(imagine the WW fighting system multiplayer), but Mario would be pretty cool too.