ok heres the loadown.

I have to wait until christmas to get super mario galaxy, my parents will not let me buy anything else so they and others in my family can get christmas gift ideas.
well, im thinking, what if i rented it?
see, the bad thing about renting games with me is, if i beat a rent game, i don't want to play it anymore.
like one time i was going to blow some money on wind waker, but i rented it instead, beat it and said "ok, i won't buy it"

im just saying, if i rent it for, oh, 7 days or so, will i get to far in it, and when i get it for christmas, will i not like it in a way?

If you rent it and play it through close to the end or beat it, don't buy it considering you can buy something else that would be more enjoyable.

I'd wait for it, you feel less rushed and enjoy it more.

well, sometimes i'll pull out my old n64 and play super mario 64 for a while.
i just might wait

I would wait! I think this is a great game, and I think you will really enjoy playing your own copy on Christmas!

Yes I agree with others, you should wait because it will be so much better on Christmas after having waited for it. And I can say this mainly because there are so many other good games out or coming out before then to rent and keep busy with.