What exactly IS canon?

[RR☆Oresama]

Okay. We all know that the games, anime and manga are all separate verses, but how about the games themselves?

Generation V told us that the events of Platinum were more canon than Generation IV, seeing as Caitlin is now part of the E4 and Shauntal talked about Giratina and the Distortion World, along with Cynthia and Looker's appearance.

But what strikes me is... how exactly are all the other games canon? Not just the main series timeline, but also, Ranger, Colosseum, and PokePark?

So far, we can all agree that the main canon is like this:
Red/Yellow/FireRed and Ruby/Emerald - 3 years later - Gold/Crystal/HeartGold/Platinum
Blue/Yellow/LeafGreen and Sapphire/Emerald - 3 years later - Silver/Crystal/SoulSilver/Platinum

And apparently, Black and White occurs 10 years later--but what happens to the third versions and all the games in the franchise?

 

[The 100 Mega Shock]

I doubt that Game Freak pay particular heed to "canon". They simply take the stories they've written and add in the bits and pieces they think would be good to put in the next game, most likely using the third versions' events because they were produced more recently and were a chance to change whatever they didn't like about the previous game.

I don't expect anything else in the Pokémon franchise to be taken into consideration either, mainly because they either take place in other worlds than the main games or they're just so far away from the other regions that none of the events that occur have any effect on the stories that Game Freak want to write

 

[Gymnotide]

I've been helping put together this page on Bulbapedia. Check it out.
https://bulbapedia.bulbagarden.net/wiki/History_of_the_Pokémon_world