I say it's all about where you want to live...for instance Pinnacle and Mesaba would be my choice seeing how I want to live in Minneapolis...but if you don't mind the commute...shoot pick any regional except Mesa and Gojets (of course).

If you are all about the upgrade pick a regional that will get you to the left seat in a hurry then start pushing apps to the Majors. But to answer the question top five:

1. Pinnacle
2. Mesaba
3. Express Jet
4. Skywest
5. Republic