I've seen a couple of posts like this on the internet and I'm not sure how I feel about it. However, I could see it happening since we already have humanized ponies. These are the actors and actresses that I think can pull off the characters. This list will only have the mane six, Spike, the princesses, the royal couple, and the CMC.
The mane six and spike will get two top choices and the others will get one.

Twilight Sparkle
1. Zooey Deschanel
I was never a big fan of her until I recently started to watch her show New Girl. I always though she was pretty, but I love her in New Girl. I think she would make a great Twilight Sparkle she's smart, pretty, quirky, and quite funny. The only problem I have is that her voice is a low, but I think she could make it higher for the role. Zooey sings as well.

2. Emilia Clark
I love her. I think she is gorgeous and I think she is a good actress despite some criticism. She is known for being Daenerys Targaryen on Game of Thrones. She has dragons Twilight has a dragon. I would love to see her as this role. Emilia sings too and has a sweeter and cuter voice than Zooey. She is a little short (5'2"). I can see her as a choice for any of the other three princesses as well.
Clip of her singing live: link
Applejack
1. Hayden Panettiere
She is the perfect Applejack. She is blonde, has green eyes, athletic, she can do a southern accent, is a good actress, and is pretty. The only problem is she is short (5'0"), but that can be fixed with the proper clothes and camera angles. She sings as well.

2. Alona Tal
I know her from Supernatural and she plays as a hunter so she is pretty fit and athletic. She sings, is also blonde, and is pretty too. She will need to get green contacts though. Here's a clip of her singing: link

Pinkie Pie/Fluttershy
1. Ariana Grande
I think she would be perfect for either of them. For Pinkie her character would be similar to Cat (haven't really watched Victorious, but I know she is quite cute and funny like Pinkie). I also think she could play Fluttershy if she just acted a little more shy. As I'm sure most of you know she sings and has a really cute talking voice. She is a little tan though and that's not really how I imagined Fluttershy, but that can be changed with makeup and the like. And of course she is pretty! She will need to dye her hair which I'm sure she doesn't have a problem with and will need contacts. She is short though (5'0").

Pinkie Pie
2. Kristen Belle
I found her on a DeviantArtist artwork: link. The artist actually had her as Rarity, but I think she would be much better as Pinkie. She has recently played as Anna in Frozen who in some ways is like Pinkie (sweet, cute, funny, etc) and she can sing quite well. She may even do as a good Applejack.

Fluttershy
2. Emma Watson
I think she is so cute and would make a great Fluttershy. I saw this on the same Deviant. Emma has a cute voice and she actually sings (I actually didn't know this until I wrote the article)! Here's a clip: link (She does the vocalizing). She looks innocent too like Fluttershy. I think she could also play Twilight since she is very smart.


Rainbow Dash
1. Avril Lavigne
I saw this on the Deviant as well and I had to put her as Rainbow Dash. She obviously sings and is cool just like Rainbow. I don't know about her acting skills, but I think she could learn and it may help her career.

2. Emma Stone
I really like her as an actress and I think she would be great as Rainbow Dash especially since she is a huskier voice. And she sings quite well if you are familiar with Easy A.

Rarity
1. Leighton Meester
She did play quite the little diva on Gossip Girl and has a nice fashion sense so I think she would be perfect as Rarity. Not to mention that she is quite lovely herself and she sings. Here's a clip: link

2. Scarlet Johanasson
I was thinking about her as another option for Applejack or some other characters, but then I saw a picture of her on Devianart and she would make a great Rarity. And you guessed it she sings. Here's the clip: link

Spike
1. Adam Brody
He is Leighton's husband so I'm sure it will be quite easy for him to act like he's infatuated with Leighton as Rarity. Also, he was just on New Girl so I think Zooey and him will be able to get along well.

2. Joesph Gordon-Levitt
I can definitely see him as Twilight's best friend and trusted side-kick especially after his role in 500 Days of Summer.

Princess Celestia
1. Taylor Swift
I know a lot of you are thinking what, why Taylor? Well for one she is beautiful and she is also very tall. I saw this picture on Deviantart and I think its lovely. I know Taylor hasn't done much acting, but I think since a large portion of her fans is young girls and girls in general maybe she would like to give MLP a try and of course she sings!

Princess Luna
1. Olivia Wilde
Her eyes are just so expressive and Princess Luna's eyes are as well. I think she is just beautiful and a fine actress as well.

Princess Cadance
1. Natalie Portman
Cadance is in my opinion the prettiest pony and Natalie Portman definitely makes my list of the prettiest actresses ever. She is just lovely and she does sing. She's a great actress too! Here's a clip of her singing at fifteen: link

Shinging Armor
1. Tom Welling
I think he is really good looking and would look cute with Natalie. He's a pretty good actor, but I've only really seen him on Smallville.

Apple Bloom
1. Chloe Grace Moretz
She is so cute and a great actress for her age. I would love as Applebloom and she would be good as probably any of the CMC. She sings. Here's a clip of her singing kind of silly: link

Sweetie Belle
1. Mackenzie Foy
I think she is the cutest brunette girl ever. She has an innocent face and gorgeous green eyes like Sweetie Belle. Unfortunately I don't know if she sings, but she may.

Scootaloo
1. Bailee Madison
I know from Don't Be Afraid of the Dark and she has grown up so much. She was quite good in the movie as a child, but I haven't really followed her career. She does sing as well. Here's a clip (Its hard to hear her though): link

So what do you guys think? Are there any actors I missed that will do the part better? I'm sorry that the cast is mostly white, but to be honest I didn't really imagine the mane six as other races. Now that doesn't mean that they can't pick someone of a different race its just that there wasn't that kind of actor or actress that stood out to me.