Real solid game in almost every single way.

Not sure why no one ever mentions this, but all the backtracking and general effort required to get all the upgrades is tedious as fuck, especially when the endgame is balanced around a fully-powered X. It's a problem that has plagued the series since, and it started with this game. It completely destroys any replayability that the games would have had, too.

Other than that (and mediocre bosses), I have no other complaints. Good level design, great music.