I don’t have enough for a top ten, but here’s my usuals/favorites in no particular order.
Northeast Wisconsin: It’s home base, plus the free KOSH airport with the EAA runway dots and famous Fisk Approach landmarks. I’m also a trucker very familiar with the major roads in the region and it’s nice to follow the highways in the sim and know where I am without needing the VFR map up.
Chicago: I often park at KORD gate F27 for benchmarking tweaks.
Grand Canyon: F-18, need I say more?
London: For when I’m in a dystopian mood.