I think starting with Zero Mission would be best. Original Metroid hasn't aged well, and ZM has the original Metroid that you can unlock afterwards anyway if you really feel like trying it, then jump into the Prime games. Hunters takes place between Prime 1 and 2 but is...not the greatest for single player, to put it lightly.
The no saving, no map, no diagonal aiming thing sucks pretty hard too
And that most of the hallways look exactly the same.
Metroid 2 for game boy is still pretty good these days but was really unappreciated for releases. Wheras the original Metroid has been released 6 different times now, Metroid 2 went without any rerelease for around 20 years (where it's now on the 3DS).
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Geologists will date anything.