It was all about expectations, anon.
You hear "MLP" and assume it will be terrible because it's a girl cartoon and because it has had a history of really terrible direct-to-video animation, but then the new 2010 version turns out to be decent.
It's just "decent", but you were expecting it to be shit, so in comparison to your expectations, it's amazing.
And that's why most people say the show's quality dropped off after S2, because by S3, the sheen of "girls show that doesn't suck" wore off and peoples' expectations were a lot higher, and they began to realize how mediocre the show was. (though it didn't help that they had a huge turnover of staff, and continue to drop old writers and add new ones, leading to a host of problems for the show)