My reasons for watching mostly come from the film critic in me. Contrary to the popular "love and tolerate" phrase, that does not describe me at all. I didn't watch this show because I have an open mind, I don't, I have a critical mind. "Love and tolerate" isn't a staple of the fandom, it's a slogan, and is as misleading as slogans usually are.
I consider myself somewhat of a film buff. I have roughly 350 films in my collection, and for the last 4 years I have been regularly watching hundreds of videos from the comedic criticism website, ThatGuyWithTheGlasses.com. My family and friends know me as a nit-pick, and my best friend and I just talk about films and story-telling all the time.
Some would think that being negative and critical would naturally mean I couldn't relate to a little pony girl's show. That is not true. Anyone who dedicates a good chunk of their life to studying entertainment and what makes it work knows that not all ideas and subjects should be judged by the same criteria. I don't hold every production to same standards as Citizen Cane, it'd be ridiculous to even try. You have to judge something on what it is, what its trying to do, how does it compare to similar types of movies or genres, and even if it fails was it trying to accomplish something but didn't quite execute it well enough. You don't compare Disney films to Shawshank Redemption, and you don't compare movies that aim to be fun with movies that aim to be topical.
That being said, the questions are what does My Little Pony deliver, who is it's audience, how does it compare to similar cartoons, how much effort was put in, and how does it compare to it's previous generations? The question isn't whether its better or worse than other television shows I enjoy because I love those shows for very different reasons. I love Game of Thrones, but I wouldn't compare MLP to it, nor even most live-action TV shows because most of them have very different subjects. Even other animated works like Avatar: The Last Airbender, something I honestly have fallen in love with, are not good side-by-side comparisons. Honestly I'm a much bigger Avatar fan than I am a brony. In terms of quality, story-telling, world-building, dialogue, characters, and action scenes, Avatar trumps MLP in every single aspect. Avatar is something of genuine artistic merrit, and strived to be this epic East Asian Hero's Journey and succeeded with flying colors.
But MLP was not aiming for that, it's appeal isn't how "epic" it is, it's how simply fun and light-hearted it is. Sometimes I like to just have some good ol' dumb fun. The art design is very appealing, colorful, and down-right cute. It's characters are endearing and most of the show's appeal is just watching their personalities play off each other rather than any real plot or story. The voice-acting is pretty good with veteran actresses who do what they do best. All and all, it's managed to create an entertaining and visually-striking kid's show that doesn't insult my intelligence or sense of good taste. It's managed to gain appeal without relying on brooding characters or pointless melodrama. It's bright, it's shiny, it's cute, and it's fun. And sometimes, that's all I want.
That being said, in regards to what it aimed to do, that is being an entertaining show for young kids and their families, it succeeded spectacularly. It knew exactly what it was trying to do, and it accidentally got a much bigger and diverse fan base then they could have expected.
And that leads to next big reason I like it: It has restored my faith in hard work and effort put into entertainment. A few years ago if you told me that they were making another My Little Pony show, I wouldn't be surprised what with all the shitty remakes and sequels out there. But unlike other franchises getting brought back, the My Little Pony franchise has been garbage for all of its existence. It's one thing to take a classic cartoon and butcher it, its quite another to take something previously regarded as poison for ratings, and turn it into something that has gained a HUGE fan base. This SHOULDN'T be possible, but it is. I cannot think of a franchise that has exemplifies an evil toy commercial more than the My Little Pony franchise. For over 25 years that franchise has been a prime example of no-effort, zero-quality, mind-numbing, cheaply-made garbage to promote crass commercialism. It didn't even sell toys to girls anymore by the mid-90's. The 2nd and 3rd generations were abandoned as failed projects by Hasbro because girls just weren't buying the toys anymore. They've moved on to other toys, and it sure as hell wasn't the cartoons keeping their interests. So when they relaunched a lot of their old franchises a few years ago, it was easy to predict that this too would be another failure in terms of show quality as well as toy sales. But shockingly, it wasn't. If I could sum up G4 MLP into one word, it would be EFFORT. Honest-to-God effort was FINALLY put into this franchise after decades of deprival. And the result is a huge fan base outside it's target audience, many of them being the most negative, nit-picky people on the planet.
If I could claim to have some "philosophy" regarding this show, as some do, it would be that it restores my faith in hard work bringing results. Just because it's a kid's show, that is NO EXCUSE not to try. If you put your mind to it, you can make anything appealing. If one of the worst franchises of the last 30 years can suddenly become a huge phenomenon, then ANYTHING is possible if you just work as hard as you can and not settle for anything less.
The final thing that's holding this fandom together is the fan-participation. Hell, most of us stumbled upon this accidentally over the internet through some PMV, fan-art, parody video, or music. There is just something about this show that seems to just inspire people to create things. Maybe the art design, while being cute, is easy-enough to imitate and it inspires people to try and create their own ponies and comics. This I honestly can't break down like I could the previous subjects. The fandom has taken a life of it's own, I don't know why, I'm just enjoying the ride.
Well, I think I've ranted long enough. I hope that answers your questions.