1st Gen Red's Starter

Which Kanto starter (excluding Pikachu) would you say is the one Red choose in the games?

I'm sure if we're going by assumptin of his name, plus the fact that he had a Charmander in Pokemon Origins, I think the answer is quite clear.

If we're going by video games, it'd be Charmander.

For the Manga it'd be Bulbasaur.

But according to the Manga series , red had a bulbasaur ! Even though we have a strong support that Red's name was kept by his father so that he could be as fiery as a flame which was the reason he chose Charmander in the origins , it is still an unanswerable question to what was red's starter due to the multiverse present in the franchise

While you want to discount Pikachu, it's hard to argue for any other starter being canon. It's his highest-leveled Pokémon in the games, it forever remains unevolved, and he has all three of the normal starters, which was only possible without trading in Yellow.

Him starting with Pikachu means that none of the other starters are favored over another and all three can be represented on his team, so it's completely neutral and unbiased. It makes perfect sense why Pikachu would be canon.

Adventures and Origins aren't game canon (the former not even remotely so), so they shouldn't factor into this. In the case of Origins, its main purpose was to use nostalgia to advertise a new (and completely unnecessary, IMO) Charizard Mega Evolution.