Think I should?
I only have to get 6 more....Radioactive Man, Dr. Collosus (with Death Mountain), The Collider, Win Lad & Citizen Solar, and The Fracker. Also Milo with Coolsville even though he's not a superhero.
There is also 5 more superhero character skins to get: Stretch Dude, Clown Face, Sidekick Milhouse, Bouncing Battle Baby, and Cyborg Snake.
As for buildings....Kane Manor (need to have for Radioactive 8 hour task), Bartman Cave, & Pies for Guns Booth.
And there is those other random buildings (that are in Springfield) that came during the Superheroes events....Spirography Factory, Springfield Books, National Bank of Springfield, Burns State Prison, Burns' Summer Mansion, Dead Lobster, and the Botanical Garden....these ones I can wait until if some return in minor or major events.