While not the best entry in the series to start with, this game definitely still has its merits.
Story
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Like the first Metroid game released back in 1986, this game has a very simple story that is certainly not immersive. However, it is necessary to understand the events of this game in order to fully understand Super Metroid and appreciate it even more. After her first mission on Zebes, Samus is ordered to pursue planet SR388 to drive the Metroids to extinction. There ya go. At the end, you fight the Queen Metroid. After defeating her, you find a small Metroid that which hatches and subsequently follows you. You take it with you as you leave SR388. That there is your story. Story: 7/10
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Graphics
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But as the original Metroid game proved, a good story isn't necessary for a decent game to be produced. The graphics in this game are far better than the original Metroid's, but with little to no color. (You can provide a basic color palette to be applied simply by playing the game on a GameBoy Color, GameBoy Advance, or GameBoy Player) The animations are somewhat mediocre, as better animations existed at the time. However, the sprites are ultimately an improvement over Metroid's NES debut. Graphics: 7/10
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Gameplay
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The gameplay of this game revolutionized the Metroid series more than you may think. SR388 supplies you with many items you can get in the original Metroid plus more. Almost all of these items are now a staple to the Metroid games: Plasma Beam, Spazer (Laser), Space Jump, Spider Ball, and many more items. Item variations are also present. The Varia Suit changes Samus's suit entirely. See, in the original Metroid, the Varia Suit upgrade simply changed Samus's suit to a darker orange. Well, this Varia Suit added the infamous shoulder guards that which everyone depicts Samus having as of today. It's because of Metroid II that such an image was made for Samus. The reason they made the Varia Suit change the appearance of Samus rather than the color was because the GameBoy could not handle any color at the time.
The main focus of the game is to track down and kill about forty Metroids. The Metroids show their true colors by displaying a few from each stage of the Metroid's metamorphic life-cycle. Thus Metroid II also brought Metroids an entirely new image with these metamorphic stages. The Metroids get progressively more difficult as you fight the higher stages. Ironically, however, you do not face the traditional Metroid larvae until near the end in a Tourian-esque Metroid stronghold. This is because you probably do not have the Ice Beam until around then---and unfortunately, you can only have one beam equipped at a time.
As for bosses, there are two; one is optional, and the other is the final boss. The optional one is Arachnus, much like Arachnus X from Metroid Fusion, though this variation of the vile organism requires a different strategy and demonstrates an entirely different behavior. Arachnus cleverly hides where you would not expect a boss, and guards the optional but extremely useful Spring Ball.
The atmosphere is nearly perfect; you are alone on a dangerous planet infested with life-sucking creatures in forms you've never seen before. Creepy, right?
New game mechanics that were absent in the original Metroid but since their introduction in this game have become staples to the Metroid saga include crouching and the ability to shoot downwards when in mid-air. Gameplay: 8.7/10
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Sound
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The music and sound effects are, for the most part, boring and do not live up to the wonderful 8-bit musical score in the original Metroid. There really isn't much music to begin with, mostly just beeps are used. Moments where actual music is implemented is when you fight a Metroid and also when you fight the Queen. Then there is the cheery music once you beat the Queen and head for the surface of SR388 with a tiny Metroid hatchling following you around. And let's not forget the credits. Otherwise, the music sucks. The sound effects are alright for a GameBoy game. Namely, the squeal a Metroid makes is good---for its time. As of today, the sound effects would be labeled cheesy. Sound: 4/10
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Length/Replay Value
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Not much. The length is satisfying but sometimes exhausting. The replay value is almost absent because of this; however, you're more likely to play through it again to kill time rather than a game such as, say, Metroid Prime 2: Echoes. Length/Replay Value: 7.5/10
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Fun Factor
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This game could very well be the weakest entry in the entire series. But still, it can be fun for a short while. Metroid fans should definitely give it a shot, but casual gamers...don't bother unless you enjoy the genre.
Overall: 7.5, good. I've never found a Metroid game to be this...well, dull. It still has its exciting parts, however, like when your health is NOT almost empty.
Ultimate Ridley out.