This is cute and charming, and I like the graphics a lot (I love the flip jump), though I don't think they really look the part of an NES game beyond the use of pixel art sprites. I do feel like the procedural generation is resulting in levels that aren't really very interesting to play, with way too many enemies to be able to take on. While it's an interesting mechanic, I think in this case, manually designed levels probably would have been more fun to play.