Pretty well done. Nailed the retro feel with the modern smoothness and flow. It reminds me of Contra with its difficulty and the intro with the shored ship is basically Metal Slug.
I'll have to agree with ryogo here with the lack of variety. It just feels bland after a couple stages.
Graphics-wise, one of the most well-done I've seen. The CRT TV look is cool, but it was more asethically appealing than actually adding anything to the game. It might just be me, but I did not like playing the game with the CRT TV "bulge" to the screen.
Having an option to turn these graphics settings on/off would be great.
Overall, pretty fantastic job. You've put a lot of effort into it and I can see it.