"In Angry Video Game Nerd episode 225, The Nerd takes a look back at the Metroid series' early beginnings with the original Metroid for NES, Metroid II: Return of Samus on Game Boy, and Super Metroid on SNES!"
He's not wrong.
The first Metroid game I ever played was Metroid II: Return of Samus (which I bought for $15 from one of my friends in middle school) on my gray brick Game Boy. Unlike the AVGN here, I did not have a Nintendo Power map, yet I somehow managed to legit finish it. Then, my next one was Super Metroid, and pretty much everything that the AVGN says about it here (almost entirely good) is all true. It wasn't until years later, after I discovered the ability to play old NES games on my computer via emulation, that I ever played the original Metroid. I'll just say this much: thank goodness for emulator save states, because I otherwise probably would have never finished that game otherwise. ¬_¬
I've played every game in the Metroid series up through Metroid: Other M (not counting the offbeat spinoffs like Pinball or Hunters). The only reason I haven't played the later ones, like Samus Returns (a remake of the Game Boy game) or Metroid Dread is simply because I didn't/don't/possibly won't ever own the consoles/handhelds on which they were released.
(Weird that I didn't have a "metroid" tag before now. Guess I'll have to go and do some backtagging later. *shrug*)