Hm...I'd like to think of it in this manner:
Design-wise:
Snivy would definitely take the crown for this one, and even it's evolutions seem to obviously carry that regal and "smug-ness" through and through. Tepig and oshawott are definitely cute, but unfortunately the same really can't be said about their final evolutions, which I believed turned most people off of them more often than not.
Funny though, I remember a discussion not so long before B/W was released when the picture of the final evolution of the starters was leaked or something and everyone was literally hoping that they were fake. I made a post then saying that in the future, probably no one would really care and pick Tepig or Oshawott anyway.
Turns out I was surprisingly correct, though I did say this happens in every generation, and it has happened.
Strength-wise:
Emboar, kinda. Serperior takes this crown also, because of it's Dream world ability. It's common knowledge that Contrary and Leaf Storm on Serperior is possibly one of the deadlist combinations in a grass-type Pokemon, which possibly could make serperior quite the formidable starter if you're facing someone who's quite experienced in it, at least.
Emboar has strength in it's typing. In a sense, it's another infernape, and a blaziken, unfortunately. I fail to see what really separates it from these two, and it seems as if the latter two outclass it anyway in pretty much everything. I'm not saying Emboar is terrible, but why must it be slow, of all things? It's a pig, but c'mon, Blatoise is a turtle and yet it's twice as fast as this thing.
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I would probably going into more detail and whatnot, but I'm feeling kinda lazy and well, my personal bias towards grass-types would probably always win above everything else, so if anything, I would've gone for snivy whether it really had the strength or not. :(