FP. Gen 3 is where the games peaked for me honestly
Yes, though gen 5 might have improved on that.
Gen 4 is also quite good, i did play D/P but i assume Platinum is better as the end version of it.
Gen 2 remakes were good as well.
Gen 1 hasn't aged that well but has a lot of staple pokemon at this point.
Gen 6 wasn't great, though it introduced fairy type. But from this point the games became too easy/less qualitative/immersive.
Gen 7 introduced some cool pokemon and had original ideas. After Gen 7 i haven't really played anymore though but from what i've seen i'm not too interested in getting back to it.
I also don't really like the gimmicks, starting from mega evolution but esp. dynamax/gigamax etc. Very boring. Esp. since you never have to mega evolve in the games because without mega evolution it's still too easy, and wasting time on the animation to mega evolve is boring and tedious while i could have 1-ko'd the pokemon otherwise.
Hoenn and Unova are my favs. Out of the first 7 in terms of introduced pokemon Johto (gen 2) probably worst followed by Kalos (gen 6). Kanto, Sinnoh are mid. Alola third, Unova second and Hoenn first).