I like Steven Universe, but as for best currently running Western children's animation, I'll jump on the bandwagon and give it to Gravity Falls, the setting and jokes just work really well for me.
MLP still occupies my #2 spot as it still provides a good mix of pop culture references, interesting high fantasy setting that isn't stuck in medieval times tech wise, and simple but interesting enough plots to keep me entertained, as well as a fascinating animation style that has noticeably and drastically improved as seasons go on.
I suppose that would put SU at around the number 3 spot, up there with Adventure Time, as far as kids shows go. Judging all Western animation messes the order up as the likes of Archer are definately up there. For me, cartoons are something I put on in the background when I'm doing laundry, cooking, or paying bills, so for me, the best cartoons are ones that can keep me entertained while I'm only half paying attention.
It is nice that Western animation has gained some great to good shows within the last few years, around 2005-2010 we were going through kind of a quality Western animation drought, it wasn't dead, but it really seemed anemic compared to the late 90's early 2000's and downright desolate compared to the early to mid 90's.