>>47452851I only ever really play Gen III and IV. Never migrated to Gen V+ or beyond, even with later games, just keeping all the teams together with those trainers. Keep almost everything from my cartridge games, and nothing for my ROMs.
Reasoning I keep all of my Gen IV stuff on my cartridges is that I see as my prized games and essentially now use them all as a big collection of Pokemon I've trained over the years. Whenever I want to make a new game, I transfer them over to my main games. Every now and again I like to boot up all my games and just look at all the Pokemon I have and remember the runs I did with them over the decades. It's really nice to go back and say hi to my old friends. It feels like I'm Ash returning to Oak's ranch after a long journey.