This is a difficult question to answer man, because Saga is so far up there in the realm of best american comics out there today. It's hard to draw comparison between other books, or anything similar. Best bet is to do what you've did, which is look at BKV's other stuff. He's working on Paper Girls right now too, and alongside Y, he has another well received book called Ex Machina. The Scott PIlgrim guy has an Image book right now too, called Snot Girl. Fiona Staples worked on Archie for a little bit but that's REALLY nothing like Saga haha and I think Saga has pretty much taken up the rest of her time the last few years.
Otherwise, have a look around at what else is being published. If it's mature different books, Image put a lot of stuff out like that, although they vary wildly in tone, genre and themes to Saga. Some of their best books right now (obviously imo) are Souther Bastards, Lazarus, Rumble, Deadly Class. Specifically Sci-Fi there's Descender, Invisible Republic, Low (although I wouldn't say any of these are particularly like Saga in tone).
In terms of just great books that have finished up their runs and are imo incredible, you could check out: Locke & Key. Sweet Tooth. Scalped.
