Season 1: While I feel it wasn't exactly finale material, it was quite a sweet, fun story the girls shared. I enjoyed it as a regular episode, but a bit of a disappointment for a finale. Can't criticize too much, though; after all, it was the first season.
Season 2: Quite possibly my favorite finale. Due to this, 'fraid I'll have to keep it at that. Otherwise I'll delve into a boringly lengthy description about the love I feel for this two-parter.
Season 3: Seemed very rushed; the problem came as fast as the solution. I think it was a mistake to make such an incredible major development in the show and not making it at least a two-parter. It's like the concept of Twilight becoming a Princess was just so overwhelming and overbearing to the writers they couldn't think of anything better to put in the episode. Not on board with Twilicorn, either...don't think I ever will. (I know, I know, I should be over it by now.) Although I will say that the music was exceptional, each a hit. An emotional episode that actually made me cry at the time, so, yes, it succeeded in the emotional factor. It had so much potential, so I suppose my main problem with this finale is simply the potential wasted.
Season 4: Mm. Entertaining. Cool storyline. I'm pretty much impartial.
Season 5: Always a fan of the concept of past/present/future altering and time jumping, very cool to see this concept in MLP. I loved seeing alternate versions of the characters and was just an overall well-developed and well-paced episode.
Season 6: Awful. Not a fan of Starlight Glimmer anyway, and the concept just didn't grab me. It seemed scattered and not presented well. The storyline was bland and so were the characters. Not to upset anyone, though.
Season 7: I thought that the finales could get any worse after what Season 6 pulled, but I was wrong. The worst out of all finales. Basically everything wrong with this finale as it were in the S6 one, only multiplied. Don't want to go on a rant about it, so I'll just leave you at that.
Overall? Pretty great finales as a whole.