For me it's the original 151 only. I wish there was a separate continuity where nothing else is canon and instead of the subsequent games being new region+new pokemon, there would be a remaster of the original game that fixes all the bugs and with better balance that would essentially be the de facto pokemon experience and then instead of a new gen every couple of years, the focus would be on new games like pokemon snap(set in the Kanto safari zone), a pokemon fishing game with Misty, a pokemon racing game , a Celadon Department store management game, a Mario Party-like, a stealth game where you play as team rocket grunt... Things like that that would always put a completely new spin on the format but it all stays contained in the Kanto universe making use of the Kanto pokemon, characters and locations in different ways.