Personally i’d say XY and gen 6 in general, mega evolutions are excellent and they made an actual effort putting lore into the games (plus i’m french so i may be biased because kalos), ORAS were imo the best remakes ever and are exactly what a remake should aim to be.
3 is the GOAT. I’m pretty sure that FireRed/LeafGreen are included in that list. The games just felt so complete and independent. I really feel like gens 1-3 were the “Classic” pokemon, 4-5 was the “renaissance” and anything onward is just modern Pokemon. The only downsides I can think of to Gen 3 is a lack of fairy type and a lack of ability to fully complete the National Dex. (I love Fairy type.)