Smith, who turned 40 this year, told Barbara Walters that the secret to his success is that "I care about people."
"I want to create things that make people feel good," he said. "I believe a big part of it is the consideration of the audience."
He also said that his work ethic plays a part.
"I absolutely positively refuse to accept anything less than 100 percent of what I can achieve," Smith said.
Smith's father was an Air Force man-turned-engineer, his mother an educator, and his grandmother, an active churchwoman. They instilled in him discipline and a desire to do well.
"You know, I had the military, the education and the spiritual all in my house and nobody accepted anything less than 100 percent," he said.
An "A" student growing up in Philadelphia, Smith started rapping at 18, and his success led to the TV series "The Fresh Prince of Bel Air," which led to the movies.
Smith's first marriage to Sheree Zampino ended in divorce, and the couple had a son Trey. Smith married actress Jada Pinkett Smith 11 years ago -- they have two children, Willow and Jaden.
Smith told Walters that "divorce is not an option," an attitude that informs their approach to the relationship.
"If divorce is not an option, we might want to figure out how [to] have some fun together since we're going to be here," he said.
"Being married is the most difficult thing you're ever going to do in your life, ever," Smith added. " Anybody who's married, and divorce is an option, you're getting divorced."
Together, he and his wife recently started a private elementary school and he also founded a church that welcomes all religions.
And if that isn't enough, Smith is starring in his most surprising role to date in the new film "Seven Pounds." In it, he plays a man at the end of his rope.
Without giving away too much about the film, Smith said that "it's out on that edge. Out on that limb."
"This character is probably the darkest character I've ever played," Smith told Walters, but added that the film is about being a good man. In his own life, Smith said, he's "trying very hard" to be a good man.
"The 10 Most Fascinating People of 2008" also features interviews with Tony-award winner and "Frost/Nixon" star Frank Langella, conservative talk show host Rush Limbaugh, teen sensation Miley Cyrus, and record breaking Olympic gold medalist Michael Phelps. CLICK HERE for photos of the full list. The most fascinating person of 2008 will be announced on the program.