I liked season three, despite how rushed it was. Obviously it would have been better if they had taken their time, but I guess Hasbro had their reasons.
My favorites are Twilight and Pinkie. As Hank Green sings, "Twilight's the nerdiest, and that goes a long way." Pinkie just grew on me over time. (And it took a good amount of time because I had to disassociate her character with the Cupcakes fanfic. I should not let my friend pressure me into reading horror, and yet...)
ETA: AHAHAHA I BEAT THE BROKEN FORUM. Sorry about the resulting double post though.