Answer :
the Greek gods were actually very close to the roman gods because they were them but with different personalities. They were different because of the power and the minor and major gods. They were worshipped because of myths and fables.
Greece wanted a power that seemed to top others gods so they came up with the idea of the Greek gods and then installed into that idea demi-gods. (ex. Percy Jackson) It took off from there and caused others to come and respect their gods over others for their might and power.
Greek Gods were different from the Gods of most other ancient cultures because they had human form. In other cultures, the Gods were in the form of animals, natural phenomena, the sun, the river, etc.