Metroid 1 on NES hands down. It is an amazing game, despite not having a few of the quality of life improvements that were introduced in Super Metroid. The setting, progression, variety of enemies, and overall mood elevate Metroid NES not only above Metroid 2 on the Gameboy, but above almost all of the NES library. I have yet to play Samus Returns on the 3DS as I'm still holding out hope to be able replay this game on the Switch, but once the next round of Metroid releases are detailed I'll take a hard look at borrowing a 3DS to get my fix if it isn't included.