>lore wise
You mean best or in terms of power levels?
I've always liked the lore of Gen 2. There's enough mystery around Ho-oh, Lugia, and the beast trio for them to be interesting, but they still feel like natural creatures.
Gen 3 you start getting into nature deity territory, Gen 4 has literal Pokegods, and from Gen 5 on we've gotten into the abstract shit like truth, ideals, life, death, etc. And on the opposite side, Gen 1 really didn't have any lore at all. The legendary birds were just natural creatures, Mewtwo was an escaped lab experiment, and Mew was just a mysterious creature from South America.
As for gameplay that's super subjective, though anyone who says anything pre-Physical/Special split is being heavily influenced by nostalgia.