I'm going to go with Powerpuff Girls.
Even though I never watched it all that often, I sincerely enjoyed it when I did.
You can argue all you like that Friendship is Magic can be enjoyed by any demo, but the fact remains (and very obviously so) that it's a show made for girls. I've only seen one episode myself, and while it wasn't necessarily bad in any sense... it didn't have much pull to it.
PPG deliberately attempts to appeal to a wide range of people, and I feel like it delivered in that respect. MLP was just a very, very strange accident.