Really old Pokémon, which ones are rare and which ones are worth trading/powering up?

I have some really old 'mons, and I want to mirror trade a few with my friends, but I don't want to get rid of them all, they're very sentimental. But which ones V worth trading and powering up?

(P.S. There's one more not in the picture, and it's a 2020 Snivy)