This is Metroid at it's finest. Fun upgrades. A detailed world that is simultaneously ridiculous and believable. A world that guides the player subtly enough to let them get lost, but not too lost. A slew of fun upgrades that have interesting uses. A story that intrigues without getting in the way. A well built item and boss sequence that is designed to be broken by clever players. And really well built and integrated action. The E.M.M.I. sections are fun, though they get a little stale towards the end. This is a must play.