RE4 Wii is singleplayer yes, but it doesn't lessen the experience any and tbh it wouldn't work as a Multiplayer.
RE:UC is a great 2 player romp though, and don't worry about 1 on 1 targetting or any calibration, it's simple use of an on screen cursor to aim with. Very accurate too.
Overall I'm loving Umbrella Chronicles, theres a hell of alot of replayability in there, and it is a nice fan service from Capcom too, there's plenty to be happy about with it.