I recently did an episode-by-episode review (http://forum.rpg.net/showthread.php?t=489807)
of the original cartoon (including the specials and movie). In retrospect, MLP was actually a surprisingly good cartoon for its era.
The writing is reasonably intelligent (romantic clichés occasionally get subverted, Wind Whistler can be The Spock without becoming a Straw Vulcan...); the setting is a rich fantasy world; the story is darker and more epic than most people seem to expect. There's a certain dichotomy between the sugary sweetness of the main cast and how DANGEROUS their world can get, giving the show a "the Disney princess move to Sunnydale" vibe.
Among the many things I appreciate about this show is Megan's character: She's both uncompromisingly girly AND a smart, competent, badass heroine, without there being any apparent conflict.
Now, it's still an 80s cartoon, with all that this entails...But, overall, it's one of the better cartoons of its era.