Basically, do you think that Super Mario Galaxy 2 will be a better game, or simply a more enjoyable experience to you, than the first one was?
Even though chances are pretty high of it being a better game, given how they're mostly improving on the good old Galaxy-formula, some people might not see it as a more enjoyable experience since it's kind of a "more of the same"-deal, rather than a completely new experience like Galaxy was.
Personally, I love Galaxy, and I think it's a fantastic game. That said, I still prefer Super Mario 64 and think it's the best game of all time. But from what we've seen of Super Mario Galaxy 2 so far, I'm thinking it may well surpass Super Mario 64 in my eyes and become my new best game of all time. Therefore, it would also surpass the first Galaxy - therefore I vote yes.
Time will tell. June is not far away :D