Actually that movie, the one with the evil red centaur thing there, was good, better than some of the later MLP stuff that came out (with the exception of FiM of course). That movie...Escape From Midnight Mountain or something, was quite dark for MLP, even darker than FiM in my opinion for the most part, with the characters being captured by horrific creatures and transformed into such creatures themselves. While it still had goofy moments, it was handled more seriously than some MLP that came later. This was the first time MLP was ever adapted as an animation and it treated its audience more seriously compared to later MLP.
Now if you want an old MLP movie that was actually bad, try the one with the cat villain, or the one where that little girl pony ran away.
I'm not saying the very first movie was a masterpiece or anything. What I am saying is it isn't as bad as some of you might think it is. It's better than the other two MLP movies I mentioned by far, and it is the closest to FiM the old MLP ever got, in my opinion, in terms of taking the story seriously and not be focused on "I'm late for the party" or "I lost the gift!" premises.
Edit: I saw the name now. It was Rescue At Midnight Castle.