The director said W is not as "psychologically heavy" as 1995's Nixon.
He said: "I don't perceive George Jr. as troubled or as psychoanalytical as Richard Nixon, although there is a remarkable similarity in their presidencies. Nixon was more ambitious in scope and time. This is more of a soufflé.
"You have to laugh a little bit at Bush's presidency because there are so many sad things in [it]. It's tragicomedy."
Stone added that the movie's portrayal of Saddam Hussein is "pretty funny".
W stars Josh Brolin, Elizabeth Banks, Paul Giamatti, Thandie Newton, Rob Corddry and James Cromwell.
Scott Glenn, Ellen Burstyn and Ioan Gruffudd are also in the cast, while Richard Dreyfuss is said to be in talks to play vice president Dick Cheney.