Okay. Well, Pinkie, Twilight, and especially Fluttershy are the prettiest ponies of the mane 6 for me. I love Pinkie hot pink looks and her excitable nature. Also, her more mature side is so intriguing. Twilight is a total nerd but still pretty gorgeous and lovable nontheless. Despite being an introverted and intellectual, she can be really passionate when time calls for it. Plus, her violet and blue colors on her body are so attractive to the eyes. And of course, her wings. I don't really care if she turned into an alicorn in the end of season 3, she was destined to be the princess of Friendship anyway. She will always be my Twily and Equestrias greatest ruler.
And Fluttershy...oh my god, she is such a beautiful angel! I love her butter yellow coat an her rosy mane and tail. Her personality is just so appealing to the of being waifu material. And the best things, too. She is sassy and assertive, despite usually being a sensitive flower! What a mare!