And what an impoverished empire that would have been without Hellenic arts and letters. Dull, dirty brick towns and bumpkin Latin writers! The West would have to look at the Celtic bards and smiths for their inspiration, if it looked anywhere at all.
On the other hand, I can see two differences that might appeal to some people:
1) It's hard to think that Paulist Christianity - or indeed a lot of other Eastern religions - would have spread to Roman masses without a common Greco-Oriental cultural background.
2) Would the pseudo-monarchs of the post Caesar era have arisen without using Hellenistic autocrats as their examples, or Hellenistic style arts and letters as their propaganda?