For those who don't know, Jet Pac is a real game made by RARE (they had a different name back then) for the zx spectrum. In fact it was their first game ever, so this has "some" classic value. The game was also featured as a bonus game on Donkey Kong 64 which is where most people first played it.
It's also quite strange that this great game took so long to be ported to flash. Well, so did Shadowgate (uploaded to NG exacly 2 days before this one).
Now, I wouldn't rate this very high for being just a port, since it's, well, a port. Since you added a feature of your own (the Rocket minigame), the game gained content and so must be rated higher for having original stuff.
Since everything is good, there's no reason to rate it any low, but I don't think a perfect score is fair, since the main game is not an original creation. The port was very well done however, so I give it 4.5 stars.