I've been thinking about this a while after watching Nintendo's press conference. When I watched the debut trailer I was happy because it was MUCH better then the "vitality sensor" and all the other boring stuff in the conference. But while I was watching the trailer I couldnt help but notice that the game looked remarkably similar to the original, except with Yoshi.
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Seriously take a look:
http://www.youtube.com/watch?v=o9pWgEp86cM
(Super Mario Galaxy 2)
http://www.youtube.com/watch?v=qA0vLrwuQHE
(Super Mario Galaxy)
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I mean seriously. They honestly look pretty much identical apart from the addition of Yoshi. I played Super Mario Galaxy and I enjoyed it, and Super Mario Galaxy 2 will probably be good but.... 
I'm not too impressed with the trailer. Lets hope Nintendo mixes up the game from the original so it wont be confused for $50 worth of downloadable content.
-Bob Cheeseball