Cobain committed suicide in 1994
Cobain's work earned $50m (£27m) in the 12 months to October 2006, compared with Presley's $42m (£22m).
Presley headed the list for the last four years. Cobain's top placing follows his widow Courtney Love's sale of 25% of her stake in his work.
Peanuts cartoon creator Charles Schulz was third, followed by John Lennon.
The cartoonist earned $35m (£19m), while the former Beatle's work took $24m (£13m).
Forbes.com said that for some dead stars, "their work, as well as their iconic images, continues to appeal to fans who remember them, and to those born long after they died".
The top 10 was made up by scientist Albert Einstein, artist Andy Warhol, children's author Dr Seuss (Theodor Geisel), soul star Ray Charles, actress Marilyn Monroe and country singer Johnny Cash.