Greeks lacked organisation. They were cool, with their philosophy etc, but they after all fell before power of Rome. And the power of Rome came from Greeks, after all (as legends say, romans were descendants from Troy, through propably they are absolutely other tribe), and after conquering them, Romans learned much from them, the whole concept of world laws, philosophy, etc. I like Greeks, too.
Plato forever! Off with Aristoteles and his heresies!
Persians rule anyway! Cyrus! Ahura Mazda! Daevas!
What gods? They were nearly absolutely the same, except greeks have personalised their deities, they believed they can interact, show themselves, etc, while romans rather believed they are divine forces, which aren't like humans.