I can proudly say I’ve beaten 4 of those on the original hardware, but it was probably around 2010 or so as an adult.
(Contra, Ninja Gaiden, Castlevania, Mega Man 1)
Same here, though I also beat Ghosts n Goblins. Honestly once you can reliably beat the first couple of stages, you can probably get through the whole game.
That one is super hard, although I definitely haven’t truly committed to an attempt yet.
Have you tried the remake?