When you sum them up like that, you make some rather tough choices.
Firstly with the unicorns it has to be Twilight, Rarity has a more interesting voice but otherwise Twilight has her beat on all front, mostly because she's the main character. She's reasonable, fairly modest, smart and caring.
Secondly out of all the Earth ponies, it's gotta be Pinkie Pie, if you asked me before she got her own episode, it would have been tough, but now Pinkie Pie has enough character to be both entertaining and actually likeable. Applejack is good too, but she doesn't have the same presence as Pinky.
Finally, it's a tough battle between Fluttershy and Rainbow Dash, with this I'll settle for saying Fluttershy is cuter in a way you just want to protect her, she's adorable and sweet, Rainbow Dash is more amusing, aggressive and is always ready with something to say. Personally I favour Fluttershy, but I must conceed Rainbow Dash is more popular with good reason.