As far as games for my Super Nintendo Entertainment System (SNES) goes, this one sits very high on the charts. The first time i played the game was at a friends house, and on his SNES, not my own.
I owned the first Metroid for the regular NES. For whatever reason, possibly b/c it was the first NES game that i purchased on my own, i always loved the game, even with all of it's back tracking and confusing world layout. I had to wait a very long time before it would see a sequal, and even though some say the sequal came in "Metroid II" for the GameBoy, i don't (and didn't) buy it. That was a game i borrowed from a friend, beat, and immediatley gave back.
Flash forward to some time in 1994 i believe, and there was Super Metroid. Like i said, at first i didn't own the game, but i knew it was out there. I think my initial reason was that "Metroid II" wasn't very good, and that is why i didn't purchase it day one. After playing several hours of the game at a friends house i was hooked. Purchased it at the first chance i had after that, and have been hooked ever since.
The story is the usual stuff as far as Metroid games go. You are a Samus Aran, bounty hunter extroidoniar. You deliever the "Last Metroid in captivity" to a group of scienctist and take off. Naturally the planet then is attacked and the metroid is taken by "Space Pirates" for their own nefarious plans. You then go around the planet collecting bits and bobs for your suit and your weapon. Thus unlocking sections of the planet that were previously inaccessable. The usual back tracking and scouring the planet for items takes place. At the end of the story you face "Mother Brain" (again) and take her down with (spoiler... wait really?) the help of your little Metroid buddy that thinks your its mother.
This game introduced many of the items that have been present in Metroid games after it. Like the "Super Missle" and the "Grappling Hook". Most all of the other game mechanics and items were polished versions of the previous games items and/or weapons.
Probably what hooked me the most with this game was the way it looked on screen. Now this is back in the day when a really well done 2-D, go right, game was king. The different environments were all complex and looked drasticly different. From the overgrown plant level, to the lava of Norfair, even the Ghost Ship, all felt really well thought out and executed. Also in this version of the game were Mini-Bosses. Besides the usual Ridley, Kraid and Mother Brian, there were other LARGE enemies to take down. Most of which you needed to use a certain item or weapon to exploit a weakness, and pretty much all of them would reward you with another/better item or weapon. Also the music in the game is wonderful. Many of the songs have been taken and remixed by actual bands and are amazing (look up Stemage/Metroid Metal).
All in all this game still to this day is in my top 10 games of all time. I regularly play through the story and enjoy it every time. As recent as this past summer fell back into the game (on Wii Virtual Console) and went through it for probably the 10th time.
If you have never played the game and are a fan of the action adventure sidescrolling game, i would highly suggest you check it out. You can probably find a copy on ebay cheap or if you own a Wii i think you can pick it up for about $8 (play with the classic controller though).