These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Norfair Ancient Ruins Area sets up the appropriate sense of dread for the area in which you fight... Not for nothing did Prime reuse the theme for the Magmoor Tunnels.
Ridley, whose theme in this game is memorable enough that it's reused as his Leitmotif throughout the series from this point on. (The theme wasn't exclusively Ridley's in this game, but it would be used solely as his theme in future entries).
Even Better Sequel: While the previous two games were good, Super Metroid is considered the game that defined the genre.
Franchise Original Sin: While it would be nowhere near as linear or cinematic as say, Metroid: Fusion, this game definitely began a greater focus on story and cutscenes for the franchise (along with Samus getting a starting monologue), which remains a contentious topic among Metroid fans. This cinematic focus would be noted in Fusion and especially Other M.
The Wall Jump gives Samus more mobility than the game can provide challenge for. Mastering it allows players to visit areas and get around obstacles that they weren't meant to.
The Speed Booster allows for "Shinesparking" and super jumping. In addition, there's the "mock ball", which allows Samus to use the morph ball at running speed. Using these abilities has allowed speed runners to skip significant portions of the game and still beat it.
Gone Horribly Right: The game's big draw and focus was on exploration and discovery. The inclusion of many secret areas as well as two secret moves(The Wall Jump and Shinespark) fostered this mindset. However, people began to dig deeper into the game than the programmers anticipated, discovering moves like the Single-Wall Jump and Moch/Machball, methods to skip huge portions of the game, get to areas in unanticipated ways, and even discover bugs that let one start the game over with full equipment. The developers grabbed the reins again with the distinctly more linear Metroid: Fusion and Metroid: Other M.
Good Bad Bugs: Quite a few of them exist. Most of them can be used for Sequence Breaking, like a bug that lets you open certain Super Missile doors from the wrong side, but one that involves equipping both the Spazer and Plasma Beams lets you travel back in time, resetting all the game's events and collectibles while leaving Samus's inventory (minus missiles) intact.
Using the Spazer/Plasma combo glitch can lead to one of three unintentional weapons.
Combining all the beams but Wave create the Space-Time Beam; with it, Samus can reset time, beginning the game again with everything but her missiles intact.
The Murder Beam (all beams) continually damages bosses to the left of the shot, making bosses that are generally to the left of you (Ridley and Mother Brain) near enough a Curb-Stomp Battle to Samus.
The Chainsaw Beam, the least useful of the three, does no damage to enemies, but breaks blocks insanely fast, making it more of a Utility Weapon than an actual weapon.
Growing the Beard: The first two Metroid games were fine games but had very noticeable flaws. Super Metroid improved everything. It had better gameplay, better bosses (including one of the most highly regarded Final Bosses of all time) and masterfully told minimalist story. It also practically defined the Metroidvania genre.
Magnum Opus: Generally considered as the best installment in the franchise.
"Why can't Metroid crawl?": a Miiverse post in the discussion forums for Super Metroid which has become a by-word for ignorance of video game history. In the 3DS version of Super Smash Bros., Samus's flavour text notes that using the Morph Ball is "much better than crawling".
The very large (for the time) scale of the game and the incredibly high number of secret passages and hidden powerups, a lot of which were unnecessary for beating the game, prompted some Metroid fans to mess with new players by talking about the hidden region of "Warfair" and the super-hidden items known as the "Wood Beam" and "Pipe Boots". With the proliferation of sites like GameFAQs that make it rather more obvious that this is a hoax, this meme has mostly died about, but it still occasionally pops up on boards filled with Metroid veterans.
Seinfeld Is Unfunny: Modern gamers will find the game to be pretty good, but they will be scratching their heads wondering why everyone acts like it completely revolutionized action-adventures games. The open world exploration may seem kinda basic and slow nowadays, but back in 1994, no game was as huge as this (it was the largest game released at that point).
Tear Jerker: The Super Metroid's Heroic Sacrifice, done completely without dialogue, is probably the saddest moment in the entire series.
Tough Act to Follow: The biggest reason there was not a Metroid game for the Nintendo 64, was because nobody could figure out how to make a worthy successor to Super Metroid. Thankfully, when Metroid Prime was released, it mostly avoided this.
Metroid: Fusion, the true sequel, was pretty much designed to improve many features from Super Metroid, while also ramping up the difficulty.
Visual Effects of Awesome: Especially for an over-20-year-old game, Super Metroid has some very detailed and very cool sprite-based graphics.