This is what I believe each Pokemon protagonist and rival had as a starter. One of these is definitely canon.

Red would choose Charmander, Blue would choose Squirtle and that means Leaf ends up with the Bulbasaur :)

Ethan received Cyndiquil, Kris got Chikorita, and Lyra actually started with a Marill. Silver stole a Totodile from the lab.

May ended up with a Torchic, and Brendan with a Treecko. Wally obviously started with a Ralts. The Mudkip either ended up with some other random trainer, or with May after she was champion.

Dawn started with Piplup, Lucas started with Turtwig and Barry started with Chimchar.

Hilda started with Oshawott, Bianca with Tepig and Cheren with Snivy. Hilbert got a Rufflet to start off with.

Rosa started with Snivy, Nate with Tepig and Hugh with Oshawott.

Serena started with Fennekin, Calem started with Chespin and Shauna started with Froakie.

And last but not least, Hau has Popplio, Moon has Rowlet and Sun has Litten.