Not bad, but...
There are a number of problems here, one would be the fact that the screen size is too small for everything, half the text is unreadable. I have a preference for sprite flashes when it comes to Mario too, so you might think about trying that sometime. And it's a little on the short side, though better than a lot of things people try to pass on here. Overall though, this is much like many first flashes, blam it and start over. Not that I have a lot of room to talk, since I don't make flashes, I just rate 'em. ;)
Oh, and as far as hoping it dosen't suck, I suggest watching it yourself, pretending someone else made it and seeing if YOU think it sucks first. If you think it does, others probably will too. You might be your own worst critic when it comes to projects like this, but that dosen't mean others won't agree with you.