Super Mario Galaxy
The demo had a ten-minute time limit, which included 7-ish minutes of opening cutscene material (which is awesome). My timer ran out just as the space-princess started explaining that I need to gather something and be a hero or whatever crap. But of the time I actually played, I can sum it up in one word: impossible.
Maybe I'm missing something, since there was no instruction manual and I was in a semi-panic to do as much as I could with the time limit. But controlling Mario as he ran across a small floating globe was one of the most difficult things I've ever tried to do. The controls are the most disorienting I've ever seen; if there's a manual camera control, that might have helped, because one minute it was overhead and the next it was following Mario as he juked and jived along the perimeter of this tiny little planetoid, changing direction relative to the planet's center and rotating and revolving and Jesus Christ! I've never been so confused.
Of course, I still cling to fanboy hope, and trust that the game's real and/or final control scheme will be more playable.