Narita Boy is a short game with great 80s tunes and visuals, a memorable world with memorable characters, fun combat, and some of the best animation you'll ever see in an indie game.
Someone mentioned Volgarr the Viking, it's a great game but you will NOT beat it quickly. You may find yourself spending hours just trying to beat one level.
Streets of Red Devil's Dare Deluxe is a fun, Konami style, 2d beat 'em up that's about as long as an arcade beat 'em up should be.
Try the Voice of Cards games, I don't know exactly how long it took to finish them but they are like mini-rpgs. Fairly easy and not that long to play through. There's three games and you can play them in any order
New Super Lucky's Tale is a fairly short game if you just blitz through it. It's an excellent platformer.
Tales from Space Mutant Blobs Attack is a short, fun game
Guacamelee is a metroidvania game that isn't super long.