I'm starting to think this thread has mixed up "obscure" with "old", everyone i knew who had a gameboy had mario land 2, and alot of kids played CTR too (better than MK64 imo)
here's a real obscure game, a real gem for PS1, Tombi! (or Tomba! in USA)
This game is seriously amazing, one of the greatest platformers on the PS1. its about a feral kid named tombi/tomba who has to get his grandfathers bracelet back from the evil pig wizards.
yeah, plotwise it is very basic, but the settings were imaginative, the characters were charming too, even if a little bit weird at times (Tombi keeps his inventory in his stomach), with some great platforming mechanics too!
but what really sets this game aside from others is the large amounts of sidequests. theres around 130 quests in the game! i have gotten a huge amount of playtime from this game!
if your computer can run a PS1 emulator, check it out! its very very expensive to buy a physical copy of the game due to its rarity!