You need Metroid 2: Return Of Samus if you're a completist. After all, this Game Boy adventure tells the story of how Samus Aran met the baby Metroid, setting us up for Super Metroid and Metroid: Other M.
Heaven help you if this is your first Metroid game, though, as it can seem impenetrable. You're dumped in a location (Planet SR388) with no idea as to where to go and no map to guide you on your mission to shoot down 39 Metroids.
It doesn't help that the black and white visuals mean many locations look similar and you may struggle to work out where you have and haven't visited.
However, these monochrome backgrounds do heighten the feeling of bleak isolation for which the Metroid series is famous.
However, once you get to grips with Metroid 2 and have broken through some of the secret passages in the walls, you'll find that it has more to it than most Game Boy titles.
With some great power-ups to collect, including the Space Jump, Plasma Beam and Spider Ball, this is an enjoyable game that isn't just for hardcore fans.