Been playing SMG for a while now, and I'm gonna go ahead and say that it pretty much mirrors Mario 64. Is it possible to get all 120 stars without outside help? Yes. In fact if you put your mind to it I think you could do it without too much "head bashing against wall" action.
However for the non-pro gamer, its usually better to be able to say "What the heck do I do with that Gold chomp?" and spend about 2 minutes online, rather than spend 30 minutes trying every possible action, path, and probably dying at least once.
So just as with M64, it is very possible to fully complete this game without any form of guide, but not everyone will want to go through the trouble of exploring every corner and secret. So don't hate on people who get hints, because at some point during your life, you're gonna get stuck on a game, and it'll be straight to the net for you.
That being said, I still have no idea what to do with that Gold Chomp... although I'm sure I'll figure it out eventually.