Not a gen per se, but Legends Arceus was a Pokémon game that I immensely enjoyed. I’ve been playing since red/blue and over the course of the last few years, the mainline games felt progressively more stale and bland to me. Sword was the last main game I bought and I won’t be buying Scarlet/Violet - I’m put off by the hidden extra fees and have lost interest in the same age-old formula of “gonna catch them all” long ago, but Legends Arceus was different enough to feel “fresh” again, with a lot more freedom of exploration, direct interaction with your Pokémon and the environment and some interesting gameplay mechanics like being able to catch wild Pokémon without fights or lure them with food (think of Safari Zone, but 3D and with all Pokémon on the same map, no extra battle screen).

The only thing that annoyed me a bit was that the dialogue was dumbed down to zero, everything important was repeated around six times per conversation and you weren’t allowed to just skip it. That however is also an issue for the mainline games IMHO, so it was to be expected.