The only recommendation I can give you about that is to make sure that whatever you choose is something you're confident you can stick with. If you don't like drama, don't do drama; the same applies to comedy, horror, romance, fantasy, science fiction, etc. etc. If you get tired of the same thing after a while, you can blend genres. If long epic stories fail to keep you motivated, do something more episodic, maybe even with a payoff in every strip
That last point is pretty much what made Flaky Pastry work for me, where the previous projects had not. Some people prefer to work on long storylines, though. The important is to find something that works for you!