VideoGame A bit uneven in presentation, but sets the standard for its genre in content
Super Metroid wavers a bit between being atmospheric, and being "Nintendo-ish". The music is often atmospheric and subdued, and sometimes there is no music, only background noises. The metroid larva making chirping noises was a great detail that made it feel more "animal-like", like a living creature even though it's a biological abomination. And there are some great creepy moments and atmospheric elements. A corpse being feasted on by small bugs, who scatter when you draw near, shortly before a boss fight. The ghost heads that keep spawning right where you stand if you stay still too long in the Wrecked Ship, before the power goes on.
On the other hand, little things hurt the atmospheric nature of the game quite often. Backgrounds sometimes very blatantly look like they're made out of tiles, the same tiles used by the foreground. Even when I first rented this game as a kid, I laughed at the "green bubbles" in Norfair, mentally comparing them to NES graphics. The "tile" problem is very noticeable in some areas, but not as much in others. And then there's the graphics glitches involving layers, such as how any time you use the X-ray Scope, it somehow looks "through" parts of the foreground, or water. Or if you lay a power bomb, any water in the room vanishes temporarily.
But these are minor annoyances. Super Metroid really shines in creating a massive, incredibly diverse world to explore. The sheer amount of visual variety not just between locations, but within the same "area", is astounding. It also makes it easier to recognize your location using visual landmarks.
Exploration, the core of the series, makes this game shine. There's tons of things to collect in the sprawling, mazelike underground, and as the game's challenge ramps up, there's plenty of reason to collect them just to stay alive. New abilities really open up the game, making distant mountains and high ledges reachable, encouraging the player to revisit locations possibly multiple times. It's also great to explore just to see the sheer diversity of the game's world.
Super Metroid is simply a polished game that remains, even 20 years later, if not the best, then one of the best of its genre, setting the standard for the genre it partially named, the "Metroidvania".
VideoGame Deserving its status
Before I check out this game, my favorite 2D Metroid was Fusion. I have seen many people consider this title as the best of the whole franchise, so I braced myself for some hype backslash. Then I realize that the hype isn't unfound; the environment is inviting and atmospheric, the control is spot on, and the minimalist story is handled quite well, even without my beloved lore in Prime series. Boss fights are tense and epic, and Samus' animation is incredibly fluid (though her jumping animation is as goofy as always). This is easily one of my favorite sidescroller ever, but it is not without issues. The game also suffers a bit of a Guide Dang It. The infamous glass tube could be destroyed by a Power Bomb, but it would be easier for players if the tube glows yellow or have a Power Bomb icon as an indication. I also wish the game allow you to mark locations where you cannot proceed so that you can go back after acquiring a new ability, that way players will not get stuck and have to visit everything again; it also makes walkthroughs easier to follow. Wall jumping isn't that bad, but by this time I was spoiled by New Super Mario Bros., the one that does not require you to face the opposite direction before you jump. My complaints might come off as nitpicking, but I am doing it out of desire that this superb game can improve. As of this writing Nintendo has announced both a 2D and a 3D Metroid. I hope one day they will remake this game and iron out its flaws. Why can't Metroid crawl? Because this is not Metroid 2. Why can't Samus crawl? Because this is not Zero Mission.
VideoGame Super Metroid; you won't even know it's linear
Even as a Metroid fan, there was something that always nagged me about considering Super Metroid "the greatest game of all time". I completely understand the frustration that people have with Metroid's style; it's a game series that requires you to backtrack and often times you ended up completely lost. The Metroidvania style is influential but I find that it's an acquired taste.
So rather then talk about why it's "the greatest", it's important to note its major strength: extremely cohesive level design. Much is talked about the exploration of Metroid but it wouldn't be nearly as effective if the game wasn't able to subtly guide you. From the the time you enter Ceres station, to the landing on Zebes, mechanics are being taught to you. Game theorists has an excellent video detailing this, but in short, the way the game blocks you off requires you to think about what you need next. This area blocked? Head left! Not jumping high enough? There's an upgrade for that.
In addition, nearly every area is well interconnected; brinstar, norfair, crateria, wrecked ship, and maridia. The developers could have easily just made areas into dead ends with only a few branches between them. Instead, bombing certain areas and exploring each crevice gives you a cyclical feeling. No longer are you simply lost; the setting is now your puzzle to solve. How you navigate the areas creates a well-paced experience.
Furthermore, much emphasis is placed on the Samus controls. Along with the Zelda inspired exploration, Metroid games feature tight controls which while a bit more floaty, handle well like its platforming plumber predecessor. I would be remiss in handling Samus' wall jump, which is probably the most iconic maneuver in the game. With it, the way you traverse levels and shafts gains a unique pace where you can either stop and "smell the roses" or blaze through with an acrobatic fury.
Super Metroid comes from a school of "Show, don't tell". That in of itself doesn't make a game good or bad. But the way it directs you has served as an influential method of game design. It certainly adds a lot to its forboding atmosphere.