Ooh, Quantum Leap also had a heavy element of comedy.

Firefly is primarily sci-fi, but also very funny. The X-Files is mostly sci-fi thriller, but got decidedly more comedic from the latter part of Season 4 on, with a couple of earlier standout episodes written by Darin Morgan. Pinky and the Brain may also qualify, if we're counting things light on the sci and heavy on…

It's tragicomedy; how funny or depressing you find it probably depends on how comfortable you are with existentialism/nihilism.