I'm going to go ahead and put forward Descent. I could very easily see it working with a scenario, or series of scenarios, in which the mane cast journeys through the Everfree Forest and the ruined castle to defeat Nightmare Moon. The game would have several players working together as the mane cast, while one player takes control of Nightmare Moon.
No.
Bad.
There are people who don't like their voices?
I think that's an update of an old pony toy. I've got absolutely no idea why I think that though. *tries to cast Summon WJMill*