This is the first time I’ve completed my National Pokedex. I completed the Unova dex and Habitat list in White 2, but got bored and didn’t finish the national dex.
It helped that I completed the Kalos dex before Bank came out, so I was mostly there. Since Bank came out, I went back to all my previous Pokemon games and gathered my Pokemon. I have most of the legendaries (thanks to White 2 being generous with them, including events). The only ones I don’t actually have are Jirachi, Shaymin, Manaphy and Phione; I traded to have them tagged.
And since Bank gives you lots and lots of box space, I’m in the process of making a living Pokedex (ie have every Pokemon available). I’ve also collected my in-game teams from all the games I’ve played into a sort of Hall of Fame, though I kind of feel bad taking Pokemon away from past trainers lol.