I think its fairly obvious I'm a fan of the show.
Here is why I like it: It's a throwback to the cartoons I grew up with. I grew up watching original Loony Toons reruns, and remember watching episodes of Ren and Stimpy, Doug, Rugrats, Rocko's Modern Life, etc. Those were awesome shows that were fun to watch, and some of which did have a moral lesson to the story.
Fast forward to when I was a teen: Cartoon Network got a bunch of new shows that were hilarious. Dexter's Lab, Johnny Bravo, Powerpuff Girls, etc. Powerpuff Girls, despite the initial thoughts of "It's a girls show", it was a success with just about everyone who watched it.
Since these shows, we've honestly had a ton of shit cartoons. Nick cartoons arguably died after Cat Dog was released. I also hate Spongebob for the record. Cartoon Network got rid of many of their original shows, replacing them with shows that were really just noise and bright colors. Part of making a good cartoon is making something the whole family can enjoy, not just the kids.
Enter My Little Pony: Friendship is Magic. It has elements of the original cartoons on Cartoon Network. It has funny scenes that adults can chuckle at as well as the kids. The animation style is incredibly well done, and a far cry away from the overly-girly show. In fact, it's really removing the gender gap for cartoons in a way, by making something everyone can enjoy, and not just having it be about "Oh, what boy pony is the cutest" or "Does my mane look pretty?". Rarity is the only pony that really focuses on the stereotypical "fashion-conciouss" girl. Twilight Sparkle is the intelligent, realist bookworm for the most part. Pinkie Pie is the carefree, lively one. Rainbow Dash is the athletic tomboy (And lesbian if you wanna make that connection). Fluttershy is the shy one (Durr). Applejack is the hard working southern girl. I can guarantee that you can relate to at least ONE of the characters, if not more.
In watching the episode "Griffon the Brush Off" the entire opening of Rainbow Dash trying to avoid Pinkie Pie is an obvious nod to the original Loony Toons, with Rainbow Dash sprinting off in fear, while Pinkie Pie just happily (and slowly) bounces up and down following ,and always seems to be there ahead of her.
TL;DR Version EDIT: Also, my wallpaper on my netbook I take to school is a wallpaper of Rainbow Dash. I do this mainly to fuck with people. I'm 27 years old, almost a senior in college, taking serious history courses. I typically wear Industrial band shirts and camo pants (ARVN Tiger Stripe, Swedish M90, urban, etc)and have a military-looking hair cut. The fact that someone the other day saw my wallpaper, looked at me, looked at my wallpaper again, then at me, back to wallpaper again? You can't buy that level of mind-fuckery.