I had tried a few times before, but the first time I actually completed Metroid 1 was just after its remake, Zero Mission. The original game was included (also as a bonus in one of the Metroid Prime).

The thing is, the map structure is the same (just with extra levels, more puzzles and ability gating). Power-ups and bosses that already existed in 1 are at the exact same spots. Helps a lot if you can just remember where important stuff is supposed to be.