I've noticed, in official arts, or promotional videos, certain characters have certain Pokemon.
Red always seems to have a Bulbasaur, and Dawn seems to always have a Piplup.
Also, would you say, there are "canon" protagonists?
If it were up to me, the female counterpart would be the canon protagonist in all the games. However, Game Freak does not work that way. Even if Leaf had been in RBGY like she was planned to be, she most likely would not have been the "canon" protagonist.
If it were also up to me, May would have a Mudkip, Kris/Kotone a Totodile, Dawn a Chimchar and Leaf a Charmander. Brendan, Hibiki, and Lucas..I couldn't really care less, they go well with any starter.
I've always thought that Dawn and May were the canon protagonists in their games, and
sadlyHibiki and Red are the protagonists of there.