Its hard but I have been trying to name anyone that had ever been a Don or referred to as a don in any of the 3 movies.
Help me if u can
1. Vito
2. Michael
3. Sonny
4. Tom(short time)
5. Frank pesantenlli(not sure of speeling at all)
6. Vincent
7. Fanucii(not sure if he was technically a don)
8. Tomansio( the guy who helped mike in sicily in part1 dont know spelling)
9. The guy who killed Vito's father not sure of name
10. The Bad Don in part III the old one with the cane it started with an L
11. Joy faza or something(I think he was a Don)
12. Clemenza I think became a Don of his own family
13. Was Hyman Roth a don?
14. The Rasado brothers(again not sure)

(the families in the first movie
1. Barzini
2.Tatalia
3. dont know
4. dont know