- Awesome Music: The surface theme of SR388, an upbeat adventurous theme, and one of the few songs in the game that has an actual melody instead of ambiance.
- Demonic Spiders: Omega Metroids, the nastiest stage of Metroid evolution. They hit hard and are very hard to dodge, and they take a whopping 40 missiles to kill. Not even the standard Metroids you encounter in the end are as tough!
- Disappointing Last Level: Phases 8 and 9 contain no upgrades, few enemies, and almost no branching paths. They're just one long, long tunnel that you follow until you finally reach the queen.
- Growing the Beard: While nowhere near the level of what Super Metroid did for the series, Metroid II made some significant improvements over the original in gameplay. The environments aren't as confusing or repetitive in design as the original and are much less cryptic in hiding weapons, and you start off with full health and your basic upgrades (Long Beam, Missiles and Morph Ball) right off the bat. Convenient Save Stations and Recharge Stations have also been added, you can crouch and shoot down instead of just straight forward or up, and the enemies aren't nearly as merciless or frequent, alleviating the notorious Fake Difficulty of the original game. It even attempted to have mostly atmospheric music in lieu of standard video game tunes, which was a tall order for a Game Boy game, but it was a surprisingly ambitious move for a video game soundtrack of the time. The new power-ups started to get more creative around this game as well, such as the Spider-Ball and the Space Jump.
- Harsher in Hindsight: You can see the underground ecosystem of SR388 gradually regain ground as metroid numbers drop. As it turns out, this isn't entirely a good thing.
- Padding: The last third or so of the game drops its non-linear aspects. Phases 8 and 9 almost entirely consist of one ridiculously long tunnel, with very few enemies until you reach the queen's nest.
- Scrappy Mechanic: The Spider-Ball is a very useful item for exploring the game, but its controls tend to be wonky, especially when you try to bomb through a ceiling wall without getting knocked off.
- "Seinfeld" Is Unfunny: The game suffers a massive amount of this, especially after the game got a 2017 remake (along with the fan remake released in 2016). Despite the game introducing many things that would become series staples like the Varia Suit's design and save rooms, it also suffers from clunky controls, locations that all tend to look the same, and various other design problems caused by the Game Boy's limitations. It doesn't help that, despite the game looking far better on a Game Boy Color and being marketed as one of the games for the Super Game Boy, the Nintendo 3DS Virtual Console rerelease uses the monochrome palette of the standard GameBoy.
- Sophomore Slump: While the game is still fairly well-regarded, most fans agree that it doesn't match up to the genre-defining standards of Metroid or Super Metroid. The main reason is simply because for all of its improvements over the original game, it downplayed its action heavy, frantic exploration into a more slow paced, linear "Search and Destroy" adventure.
- That One Level: Almost the entire second half of the game could count, but the second half of Phase 8 (also known as Area 7 in the remake) is especially aggravating. The player has to fight 3 Omega Metroids in a massive maze with only about 5 enemies to grind for health from. It doesn't help that the last health recharging station is in an entirely different area, several minutes away.
- They Wasted a Perfectly Good Character: While it would make sense considering Samus drove them all to near extinction in this game, the various alternate Metroid life cycles never get shown again in any game since, the sole exceptions being the Omega Metroid and the Metroid Queen, as well as the various forms in stasis in the Restricted Laboratory in Fusion. All other Metroids in the series are the base infant forms, despite their evolved forms looking vastly different. In games where Metroids CAN change form, they have vastly different forms compared to this game, usually with some sort of justification. Many are interested in seeing how they would look and fight in 3D. Somewhat justified in that this is the only game where they exist in their natural environment; in almost every other Metroid game, the Metroids that appear are clones, presumably with their life cycles truncated as a result. Additionally, Fusion implies that the evolution process seen in this game only seems to work in the same conditions that exist on SR388, hence the existence of that station's Sector 1. Prime 3 explicitly states that the Metroids in that game are different due to Phazon exposure.
- Ugly Cute: The Metroid hatchling. One one hand it's a jellyfish-insectoid larva that looks no different from the standard Metroids. On the other hand, the way it considers Samus its mother and how helpful it is in escaping the final area has endeared it to many fans.
- Vindicated by History: Rather paradoxically, while the release of both a fan-made and official remake has caused most fans to view the original game as outdated, it has also sparked another fan movement that regards this game in a whole new light. For years, Return of Samus was viewed as a Sophomore Slump in the series, with narrow cramped level design, an emphasis on combat rather than exploration, a long endgame area devoid of any enemies that felt like mere padding, and a soundtrack that attempted to be atmospheric but instead largely ended up as unmemorable and ear-grating. Especially after the release of Samus Returns, some Metroid fans have started to look back at this game and argue that it is an underappreciated masterpiece where every aspect of its game design (including those commonly regarded as flaws) were actually deliberately chosen to serve the greater purpose of atmospheric storytelling. Some more extreme critics even go so far as to say that neither remake was able to capture what made the original so brilliant, and any aspect that the remakes changed only demonstrates the developers' inability to truly understand the source material. Examples include this AM2R review and this Game Maker's Toolkit video.
YMMV / Metroid II: Return of Samus