The first Metroid is easily an 8.5/10 for me. It ALMOST captured the feel of the original LoZ - but somehow the lack of map made it way more frustrating than
DUDE I was looking for my maps, graph paper and all; same score, 8/10!
It was like Zelda; no map, but you're exploring space instead of Hyrule. I LOVED that. The ambition was higher than the technology, which almost always proves beneficial once technology catches up.
I prefer Super Metroid (what I'd consider far and away the series' finest hour, still to this day 26 years later).