TL;DR: I feel like it's kind of unnecessary to complain about the obvious shortcomings that the Game Boy imposed upon this game. I feel it's much more useful to consider the benefits of this game being on GB, that being that it adds to the atmosphere that you can't properly see the screen, and how the backgrounds are so dark. Interestingly enough, this means that the original Metroid II has a better, more faithful ambience than Samus Returns, and some ways even AM2R.

That said, this game is a frustrating play, despite being on the better side of early Game Boy titles. Wouldn't really recommend trying this over replaying Samus Returns or AM2R unless you're a really die-hard fan.