The greatest SNES game!
The game starts off by bringing you up to date on the simple yet deep (enough) Metroid history. "The last metroid is in captivity." This metroid is captured and it is up to you to go and recapture it. OK, so if you're looking for a deep story then this may not be your type of game but having said that, no other game has even come close to bringing more emotion from me than the final boss fight.
This game has gone on to inspire several stellar games including the current crop of Castlevania games with it's "gain new ability to advance to the next area" gameplay. The game does feel streamlined yet it does encourage players to explore the environment for weapon and health upgrades.
If you have not played this game then I suggest you do yourself a favor and pick up a copy or download it for your Wii. Nintendo, please do all of your loyal fans a favor and port this game to the DS.