Honestly, when they first came out, the only starter I didn't care for was Froakie.
At that point, I decided to go with Chespin, as the other two really didn't stand out.
Once we got to mid evolutions, Braixen's blatantly feminine design turned me off, and while I thought Quilladin's design was a bit dumb, it was pretty entertaining and I didn't mind. I realize that chestnuts...open up after a while, so I felt like its design would do the same (it does, obviously) leading me to still keep it in mind.
But Frogadier was a pleasant surprise. The sleek, fast look is ironically how I like to play any other game (Ven from Kingdom Hearts, a rogue/archer in fantasy games, sniper/assassin in shooters), but I have had a history of liking bulky starters: Venusaur, Feraligatr, Swampert, Torterra, Emboar.
Now that we got to the final evolutions, I am actually very torn!
I like Chesnaught's design, but I feel like the coloring looks weird. I also don't like how the typing trio of Fighting/Psychic/Dark doesn't balance them out, like we were originally lead to believe (but then again, there was a type switch/mistake in info.)
I am a HUGE Dark-type lover, and Greninja's design is a pleasant surprise once again. I don't understand all the hate on the tongue design. People keep saying it's "digusting," but I have NO IDEA how a frog using its tongue is disgusting. The neck scarf is the most creative design on a Pokémon in a VERY LONG WHILE. And it actually looks cool.
Now...Delphox. The design is okay. The typing is very interesting, but other than that...I find its whole thing to be a bit lackluster. I'm just not impressed. Oh well.
That being said, I will have to find out if you really get Shauna's starter at the end of the game. If so, I will choose Chespin, but if not, I will be very happy with Froakie!