Ravana is normally referred to as the demon king with 10 heads and is generally accepted as the villain. But all facts about Ravana have been distorted by Hindu writers over the ages and I suppose even the Ramayana written by Valmiki is certain to have had a lot of interpolation.
Ravana was the king of Sri Lanka and historians have been able to place his reign during 1800-1600 BC. One thing is that he is a real character and not a myth. But there are certain facts about Ravana that can be surmised.
a) From all accounts Ravan was a very virile man and conquered many women. His favorite wife was Mandodri and an Apsara named Hema. Ravana also desired Sita in her earlier birth as the sage woman Vedavati. Ravana was struck by her beauty and proposed to her. On being rebuffed he tried to force himself on her, but Vedavati to escape the amorous advances of Ravana entered a burning flame and killed herself. She was reborn as Sita the wife of Rama to take revenge on Ravana
b) Ravana was also a follower of Shiva the omnipotent Hindu god. He is reported to have met him at Mount Kailas in the Himalayas and Shiva had blessed him with knowledge, wisdom and power. Ravana had been given the celestial juice of immortality by Shiva.
c) Ravana in his previous birth was the gate keeper along with his brother Khumbkaran at the abode of Vishnu as Jaya and Vijaya. It was on a curse that he was born as Ravana and was supposed to be an enemy of Vishnu. Rama was the 8th incarnate of Vishnu.
d) Ravana was also a man with infinite wisdom. He had mastered the Vedas and all the Hindu granths. He had knowledge of the three worlds.
Ravana was thus no ordinary mortal. He was a man with a mission. He was not a god but the epitome of the essence of man and thus had all desires and follies of a human being. His kidnapping of Sita is an act for which he his generally condemned. But in the age in which Ravana lived, these were normal occurrences.
Ravana is revered as a god in a lot of places. But one aspect not touched by Hindu writers is as to what happened between Ravana and Sita. What was the relationship? It is mentioned that he visited her everyday with gifts and presents.Surely a relationship spread over many years cannot be restricted to only flowers and gifts. It is also mentioned that he was a very virile man. But everything else is in the realm of conjecture.