The flaws of the original Metroid are well apparent: despite being a pretty small map, the visual similarity of hallways makes it a real maze to navigate (especially without any in-game map) and the ridiculous amounts of random wall-bombing needed to progress make the game less of a puzzle and more tedious brute-force trial and error.

That being said, while it wasn't executed perfectly, the core idea here is so brilliant I'm willing to forgive a lot of that. On top of that, the visuals, music, and general mysterious atmosphere are executed so well, and are such a radical departure from the other games Nintendo was releasing at the time, that it real feels like you're playing something special. Don't get me wrong, Super Metroid absolutely blows this out of the water, but there is still the germ of that greatness within the original game.