This is a rather subjective question; however, you could answer it this way:
The ancient Greeks developed an advanced civilization largely due to their ability to band together for defense and their ability to learn as they traded with others both within and without their culture. Early Greeks formed city-states due to their geography, but in order to keep from being wiped out by neighboring tribes and kingdoms, had to band together. This eventually led to the formation of their democracy. Overpopulation lead to the early Greeks migrating and trading within their country, and later throughout the region. This exposure to different ideas, technologies, and ways of life helped to form them into an advanced civilization. So, due to factors like geography and trade the ancient Greeks were able to develop an advanced civilization.
Also, you can refer to the reference link if you need an answer that refers to a specific era in Greek history.
Great question and one that is important. Here are a few factors:
1. They developed a new style of warfare and because of this, they were able to defeat a lot of people (hoplite warfare).
2. They were also good farmers and were able to live off the land.
3. They were able to create great cities that fostered community. Many cities also had great civic pride, always something necessary for cities to grow.
4. They also developed great architecture many of which can still be seen.
5. They also excelled in learning. Think of their luminaries - Plato, Aristotle, Euripides, Sophocles. We still read them in school!
In short, the Greek were an amazing people.
IF YOU WANT TO FIND THE ANSWER YOU HAVE TO GO TO YOUR MUM AND SAY CAN I HAVE A LONG KISS ON THE LIPS PLEASE?