It would only look worse than Uncharted during splitscreen play. Putting splitscreen in isn't suddenly going to make single player look worse.
So, if it's like WipEout HD, and they just reduce the framerate and visual quality during splitscreen play, so be it. At least then there is splitscreen play. WipEout HD didn't lend itself to it very well, since it's a game about travelling at speeds of 500 km/h along a narrow track (with great graphics and effects), but it was still functional, and while it wasn't as polished as single player, it worked.
I'm not saying the single player campaign should have co-op of any kind, that's ridiculous. It's Nate's adventure, he's usually alone. But with the co-op campaign which has three people playing anyway, why can't two of them (three is a bit much) be on the same system?
Actually Kantor your wrong. The engine has to be designed differently. I'll explain. Halo 3 1 player has the same amount of onscreen enemies as 4 player splitscreen. Because it's a campaign coop. So all the set pieces etc are preset. So the engine has to be able to deal with 60 enemies onscreen with 4 splitscreen going on.
It's not as simple as taking out some texture res and dropping the resolution. They have design the whole engine to work properly. So that means less objects in singleplayer, less charatcer detail etc.
Dude Naughty Dog have already stated to have local COOP in Uncharted 2 they would have to take a hit in graphics. Your not gonna argue with Naughty Dog are you? If it only affected graphics for just the coop then their reason for not putting it in the game does not make sense. They arent putting it in due to the engine needing to be changed. See?!