Apple is #1. No question. I don’t even eat any other type of pie. Boston Creme is #2 but it’s really a cake so I don’t know if that counts.
Also, I’m in agreement with Plaschke (which is pretty rare) that those Hostess Pies aren’t half bad. If you don’t know what they are, they’re those little pies that kinda resemble a small calzone and have a thin glazing on them.