You can play Metroid II on a GBC, GBA, or SP... and I can't remember about Micro. I bought my copy for about $15 (Player's Choice edition) in late 1998, because the GB Color was my first handheld system. Technologically, it is a remarkable feat. It's also an interesting "missing link" between Metroid and Super Metroid.
Although I respect Super Ghouls 'n Ghosts, it is not a game I want to play again. I'm also not keen to pay $8 for a game in which I probably can't beat the first level.