Just do yourself a favor and play the remakes :P
The remakes are far better, that's true lol.
However, I feel like both of these old, archaic, cryptic and slow games have a lot of mojo in them, and while both have strengths and weaknesses, I really do like both. They have a place in my heart and I will keep playing them every now and then. The first one is still cool to this day, even though half of Norfair and Brinstar look the same, but the kick-ass music alone makes me want to hop in once again. The first few times I played it I got lost so bad, obviously, and this is heavily annoying and frustrating, but once I managed to make my way through Zebes, it was awesome. Especially when you have a couple of energy tanks and missiles it gets a lot easier. The second game is nice as well, I remember playing it during long car rides. Hunting down one metroid after another is amazing and quite scary with this creepy atmosphere and music. I got lost here, too. Of course. But after several attempts I reached the metroid queen and the battle was immensely intense. Plus, it introduced the coolest upgrade ever, which of course is the Spider Ball.
Metroid: Zero Mission was a huge step upwards and is indeed superior in every way to the original, there's no doubt about that. Not much else to say other than it's a fantastic game even to this day. Metroid: Samus Returns is a pretty good, too. But what bothered me a bit is that it relied too much on that counter attack move during battles. Almost every single enemy must be defeated in the same pattern: let it approch and attack you, then counter and shoot. This gets old after a while.
Gameplay > Graphics
Substance > Style
Art Direction > Realism