LogFAQs > #965135585

Going to suggest some Mega Drive games I used to enjoy
Alisia Dragoon - Amazing action platformer, was really happy it was on the Mega Drive Mini
Ex-Mutants - Beaten this several times, not the best game but I still had fun
Gauntlet IV - The series isn't really that obscure, but this was a really good one with a quality Arcade mode and a Quest mode that is a sort of RPG
Global Gladiators - McDonalds platformer which was surprisingly good
Hellfire - Amazing shoot em up, my favourite for the system
Mega Turrican - If you haven't played anything in this series before, I recommend giving it a look, the first two games were also on the system as Turrican and Universal Soldier (which is an edited Turrican 2) and SNES got a game as well
Ranger X - Great action game which I wish was better known, I've never actually found more than a couple of people who played it
Radical Rex - Was also on the SNES, I have that version on Steam, but Mega Drive was the one I played
Red Zone - Like the Strike series but more technically impressive

And while not a short game depending how you are with the puzzles, look up Puggsy as well.