My first official analysis:
First off, I would like to put this in one of my favorites because of:
A. The difficulty of the medal challenges
B. How awesome it is to see all those bullets passing you, wondering how you live through it all
C. How awesome it feels that you got the hardest challenge in a couple of days.
Secondly, love the choice of all the characters. I used NoLegs most of the game, but when I got to the final character by amount of enemies defeated, it helped me finish.
Finally, love the music and backgrounds, especially in the final 5 levels.
Overall, it's a great game and great challenge. keep up the wonderful work. :)