It is important to keep in mind that when a people group borrows something from another culture, the people who do the borrowing make it their own. In other words, the borrowing is mixed with their own culture, so that things become new. So, even if the Greeks borrowed ideas, these ideas can be considered new in a sense.
With this said, the Greeks were different in several different ways.
First, the Greeks never formed an empire or unified kingdom. The Greek instead had a number of city states (poleis) during the majority of Greek history. Moreover, theses cities fought against each other.
Second, the Greeks never had a king. This was very different from most of the ancient people groups. In fact, the Athenians formed something very innovative - democracy. This can be judged as arguably the most radical departure from the norms of the ancient world.