Great Potential
For your first flash game, this isn't too bad. With a little bit of polishing, I think this game could be really kickass.
First of all, the graphics on the guy is pretty good, but I felt the rest of it could have been better. The rings are okay, but the platforms look pretty awful. The background seemed kind of boring and disorienting if I accidentally flew out of view of the rings or a platform. Something simple like a few layers of clouds on the bottom edge of the screen would probably make it look better.
The sound was okay, but the ring sound from Sonic the Hedgehog seemed annoying as hell. The music was a little boring. However, the jetpack sounded really good!
I felt there was really no point in a scoring system. As long as you went through the ring, you got the points. Maybe make it so you have to fly through the rings in a specific order to get points from them. That would certainly add more of a challenge.
All in all, this a good start to a pretty sweet game. Hope my critique can help you improve upon it!
-T.