I definitely go back to replay the games that is only if I manage to snag all the versions of a set of games. It just gives me a chance to play through the game with pokemon I've never used before as well as re-experience the world of those games and the story. I just find it fun haha.
Platinum is my all-time favorite video game and I used to play it over every couple months through high school. I'm three years into college and the only game I've replayed since freshman year is Pokémon Conquest, but I'm so begging for the potential Sinnoh remakes.
I've actually contemplated running through Sinnoh again very recently, as almost all my favorite Pokémon are from generation 4. I just have a lot going on and haven't gotten around to it.
I replay all the gens all the time. I even tried speedrunning Pokemon Y a couple of times, but I just wasn't cut out for it... I usually get around 6hrs 40-50m, but the record is something like 3.5 hours. I would like to get under 6, though, so I'll probably keep at it until I do, then move onto something else
Pokemon G/S/C and Emerald are a guilty pleasure of mine. These games are the apex of of the franchise. I personally believe Gen2 was the best the game had to offer since it offered so much to the series but Emerald is by far the best. I feel modern Pokemon games don't offer as much in terms of feels.
Heck yeah. Currently without a 3DS or Switch, but even if I had those now, I would still play my older games. I often restart them after a long period of time. Currently I'm playing Platinum and PoKémon Masters. Also playing Colossuem & XD for the GameCube but gotta stop by my local alternative game store to get a new controller since my last broke. And when it comes to the older PoKémon stuff, I also enjoy the older movies too.