For me it was also the generation I got into competitive battling. In-game I tried to EV (and failed!), I learnt about natures and why Adamant Herdier and Sawk was a good thing, and why Modest Audino didn't really achieve much... I also learnt most importantly how creative GF could truly be. Out of all the generations, this is the one where I literally got so involved with the world, even though things like rotationals and triples weren't amazing, it was just the little things, like... the music, the areas, it just made me really appreciate what GF were capable of, something that I haven't done with any other game.
I also learnt in way, that... if I were a Pokemon trainer, I would respect the Pokemon and actually like, ask 'em if they'd rather be free. I hate releasing but... sometimes its better like, if I legitimately was a trainer I would be a lot like N, who I think personally taught a lot of fans of the games to appreciate the Pokemon a lot more than they did before. Pokemon are individuals, and in a way, represent animals in the world, as well as people. We should all treat them the same, and just not use them for certain things... just be aware of them really. I know it's corny but N was useful I swear!!!