Launch games are always a strange mix of games that are developed, at least in some part, by the hardware manufacturer. Some of the games have to be exclusive to entice people to buy the new thing instead of just getting the game on something else. It also helps if the games showcase the new hardware... a bit like how Pikmin showcased the Gamecube's graphics. Or how Wii sports showed off the motion controls.
The big blockbuster games don't want to go for release time of a console because they usually don't want to be exclusive. They also need to sell huge numbers at launch in order to make the whole thing profitable. When consoles launch there just aren't as many consoles in the market as a blockbuster game would want to sell.
ugghhh to be fair these new generation piss me off because the main reason for the next gen is for improved visuals but honestly they look great enough as it is( understandable with the wii though) but yh i think the main launch titles will be new shooters, perhaps assasins creed and they will get their sports titles too, but to be fair launch titles nowadays mainly aims to attract the casual players which annoys me because these casual gamers is sending the industry in the wrong direction. i wouldnt expect long running series i.e final fantasy, resident evil etc until some time into its lifespan.
Yes the visuals are a big part. You have to remember that companies maybe are already planning for there next gen games and tech. So they will be some of the first games to come out. Also the wii u has probably the best realease window line up i 've seen when you consider third party titles like tekken tag and AC3 to mention some.