Small correction, I believe pompey was never made dictator

https://www.reddit.com/r/AskHistorians/comments/4tmfsd/why_is_augustus_considered_the_first_emperor/d5irsbs/

https://www.reddit.com/r/AskHistorians/comments/2u0zvm/why_is_julius_caesar_not_considered_the_first/co5duoe/

These answers by /u/xenophontheathenian and /u/alriclofgar explains why we don't consider caesar to be the first emperor