Both are practically the same with only some lite differences. The Romans pretty much copied Hellenic polytheism and simply changed the names.
Neptune was the god of water and the sea. His Greek equivalent was Poseidon.
The belief in many gods and goddesses is called polytheism. It is a common feature of many ancient religions, including Greek, Roman, and Hindu polytheism. Each deity is often associated with specific aspects of life or the natural world.
Many religions practice or practiced polytheism, including the ancient Greek religion (which is still practiced today), the ancient Roman religion (mostly based on the Greek religion), and many indigenous religions.
Greek Polytheism
Greek Polytheism
No, it is monotheistic.
Greek Polytheism
Greco-Roman Paganism/Polytheism.
Neo-Pagans worship the old gods. Modern Greeks and Romans are largely Christian now.
Polytheism: the belief in or worship of more than one godorigin:French polytheisme, from Late Greek polytheospolytheistic, from Greek, of many gods, from poly- + theos god
Leonidas was an Ancient Greek, and as such was a 'pagan' in a broader sense, but more specifically he believed in the ancient Greek Gods (i.e. Zeus etc.), which I would call Graeco-Roman Polytheism, but you can call it what you like.
Polytheism.