The Midrash on Parshas Noach tells us that although the people of Noach's time did not live in Gan Eden, they had a life-style resembling that which existed in Gan Eden. For example, the people before the Mabul possessed enormous physical strength. They were giants and were able to lift cedar trees out of the ground. They lived for hundreds of years and needed to sow the land only once every forty years. Moreover, the climate before the Mabul was always pleasant and spring-like every day. It was only after the Mabul that Hashem created distinctions between hot and cold seasons, as indicated later in our Parsha (בראשית ח:כ"ב).
Upon realizing all the pleasures that they had, the people felt that they didn't need Hashem anymore, since they had everything they wanted. They thus abandoned Hashem and practiced idol worship. They became murderers and robbers. They engaged in abominable sexual behavior by doing things like trading wives and legitimizing relationships between people and animals. People were thieves to such an extent that many feared that their clothing would be stolen right off of their bodies. One lesson we can learn from all this is that terrible things can result from having too much wealth. Once these people had everything they wanted, they forgot about Hashem and went against His ways.
Once we understand just how wicked the people of this generation were, we can appreciate the greatness of Noach. He was constantly subjected to taunts and criticism for his righteous behavior. Even while he was building the ark, people were making fun of him because of his "fantasy" about a big flood. Noach was a Tzaddik who was blessed by Hashem for his strong belief even in the face of criticism and ridicule. It is because Noach lived among such רשעים and still maintained his righteousness that he was such a great Tzaddik. He had passed Hashem's tests and resisted the challenges of his fellow men.
The same types of challenges often confront us in our society, whether in school, at work, or in social settings. If one person decides that he is not going to speak or listen to Lashon Hora or that he is going to spend his free time learning instead of doing other things, he will often be ridiculed by his peers, just as Noach was ridiculed for doing the right thing in observing Hashem's will. Doing what is right often means that one won't be very popular. We can learn from the story of Noach that following Hashem's ways is more important than being popular, and that a true Tzaddik is one who is able to persevere despite what others may think.