Tolkien Sauron. Like Sauron, the Garleans want absolute order, to rule over E V E R Y B O D Y. Plus, as far as empires go, the Garleans aren't the cool kind.
I guess that all depends on what lengths empires go to to gain their supreme rule over so many nations. My guess is most of them say, "Join us or die." Hence, Garleans.