I don't know. I think there are always people who say "The one *I* started with was *BETTER!*" no matter which franchise you view. There probably were Pokémon fans as early as Gold and Silver that said "But I liked Red/Blue/Yellow BETTER!"
I'll guess it didn't get noticeably bad till Gen III though. That's when things really started to change. The original Gameboys were gone, graphics significantly upgraded (not just color), a whole new region far from Kanto and Johto, a whole slew of new game features like berries and contests, villains besides Team Rocket, etc. If people weren't upset over the new color and 100+ Pokémon in the Pokedex, I'm guessing they were by the time Ruby/Sapphire rolled around.
No, it started on gen 3. Everyone was kids back then and were still looking forward to more Pokemon. I don't know anybody that hated gen 2, but only now people are hating other generations after gen 1.
Idk I was a baby back then, but I'm pretty sure it started sometime after the 2nd gen. I played fire red and heart gold and I thought they were pretty good. I kinda like the new games better than the old ones not just because of the better graphics. I like the new pokemon, they are cooler in my opinion. I hope I don't start a gen. war for saying that.
