I'd say adult cartoons are a separate category. They're very different things.
I find ponies better than all of those, obviously, since I associate with it the most. I only really like Adventure Time and Gravity Falls, but neither enough to watch every episode. Regular Show lost it's charm pretty fast with me and I can't stand Steven Universe. I thought it was alright at first, but the more I see, the more I don't like it.
I think the reason for me is pone just has lots n lots of likable characters. I like almost every pony that isn't Shining Armor. Even one-off villains are likable, which is almost never the case in other cartoons. There's no character I really attach to in Adventure Time, I just like the style of humor. Gravity Falls has a couple, like Wendy, and the main two characters are charming. Regular Show characters are too one dimensional. And I dislike most everyone in Steven.
Pone also has the most interesting world. It's surprisingly fleshed out for a kid's cartoon. DEEPEST LORE.
Also ponies are cutest.
And also best animation.