All of these starters have Protean/Libreo as their ability.

I ment which of these is your favorite

Cinderace is my third favorite Pokemon

Wdym they all have Protean abilities? Or are you talking about secret abilities?

Greninja is pretty cool, I like him. Meowscarada is definitely second. Cinderace isn't bad, he's just not as imposing as the other two.

Greninja is my all time favorite Pokémon

This is very hard choice, but I will have to go with Cinderace

Cinderace is the only one of the 3 I've actually used (the other 2 were mostly showdown only)