To be a history dork, the empire lasted long after his death. His govermenty things were to let the locals govern themselves and not impose on their culture which allowed the empire to stay intact.
Julius Caesar wasnt any more impressive than the other Roman leaders except he is more memorable because of his death. I dont think the list is limited to leaders but expanded to historical figures who helped shaped their nation.
Forgive me for saying this, but it sounds like you don't know your Roman history very well.
Julius Caesar was a key figure who arose to prominence at a key turning point in the history of ancient Rome. The Republic was becoming an empire, and Caesar understood that the old ways of doing things weren't going to work any more; this large, geographically dispersed empire needed more efficient centralized governance than the old, complex Republican system could provide. Thus he set about changing and reforming Roman government, and was one of the few people around with the talent and force of will to do so. The man even reformed the calendar, for cryin' out loud!
Caesar excelled at just about everything he set his mind to--generalship, governance, law, writing, even the seduction of his enemies' wives

. Which is the main reason he was killed: the little stars can't shine while the sun is hogging the sky. His death was remarkable, but it's certainly
not the only reason he's remembered.
Oh, and he also killed a lot of people, which means he's in good standing with almost all the other leaders included in Civ. Gandhi, in contrast, is all the more remarkable for being one of history's few "great leaders" who
didn't do that to achieve his ends.