I think there's another reason Kid Icarus hangs around in the memories of Nintendo fans, but it's sort of long... Nintendo's NES era first-party platform and adventure games are very closely related, conceptually. This starts with Super Mario Bros and The Legend of Zelda being developed simultaneously by the same team (R&D4). Miyamoto's team would come up with ideas first and then decide which game they would fit into better. Both series have continued to refer back to unused ideas from this process when making later games, well into the recent past. I think this creates a sort of "spiritual" connection between the two franchises, but there are also cases of visible cross-talk between them. For example, the pakkun flower ended up in both Super Mario Bros (piranha plant) and The Legend of Zelda (Manhandla), and the whirlwind-summoning recorder from The Legend of Zelda later turned up in Super Mario Bros 3. Then you have oddities like the Western version of Super Mario Bros. 2, which most here probably know was initially released in Japan as Yume Kojo: Doki Doki Panic. However, before that, it was initially envisioned as a vertically-scrolling two player platform game (sounds vaguely like Ice Climber), starring Mario. So "Super Mario USA" really just brought the game full-circle. In the process, it brought a certain amount of exploration and item collecting into the Super Mario series, which would continue with Super Mario Bros 3 and Super Mario World. Adventure of Link and the Star Tropics games both found ways to do the reverse, bringing platforming action to the exploration and tool-collecting formula of the Zelda games. Metroid was developed by a different team--Nintendo R&D1, who had developed the aforementioned Ice Climber--but it wasn't created in a vacuum. Apart from the shooting-based mechanics and the sci-fi motif, the game concept is very similar to the general concept behind Zelda: explore a single, large, interconnected map in a largely non-linear manner, collecting items to become more powerful and gain access to new areas. But it also does this entirely in the format of a scrolling platformer. Intuitively, this makes Metroid a close cousin to what R&D4 had been doing. R&D1 also developed Kid Icarus, which is considered sort of a "sister" game to Metroid, much like the first entries in Super Mario Bros and The Legend of Zelda were sister games. Like Metroid, it is a platform game with the action based around a shooting mechanic. It also involves exploration and collecting items. However, where Metroid is a non-linear exploration-based platformer, Kid Icarus is a largely linear one. It's built around upward vertical scrolling, like R&D1's own Ice Climber. The horizontal axis "wraps around" from one side of the screen to the other like a flattened cylinder, exactly as it does in the vertical sections of Doki Doki Panic. It has currency and item shops like the Legend of Zelda. Basically, even if Kid Icarus didn't really take off enough to become more than a cult classic, it is every bit a part of the same soup of ideas that was brewing at Nintendo during the mid-to-late 1980s. It is fundamentally tied to all of those other games that ultimately did become lasting mega-hits. And I think that makes it feel like it ought to be an important classic, even when we recognize all the little reasons it wasn't as successful and endearing.