Ledger trounced his rivals, picking up 95% of the vote in the AOL Moviefone poll.
His villainous Joker, in the latest Batman movie, has already been tipped as a sentimental favourite for the best supporting actor award at the coming Oscar ceremony.
Ledger (28) was found dead on January 22 in his Manhattan apartment from an accidental overdose of prescription drugs, including powerful painkillers oxycodone and hydrocodone and anti-anxiety pills.
The Dark Knight, the final movie Ledger completed before his death, also was voted best superhero movie and best sequel in the poll.
It also blitzed the competition in the movie most worth your cash category, picking up 72% of the vote ahead of Iron Man (14%), Indiana Jones and the Kingdom of the Crystal Skull, Sex and the City and Wall-E (five% each).
Ledger's co-star Christian Bale was voted hottest leading man, but also won the less flattering category of the summer's most sensational news story over accusations he assaulted his mother and sister.
The scene in which Bale's Batman flies out of a Hong Kong skyscraper was voted best action sequence.
In other categories, Sex and the City was voted best chick flick, Tropic Thunder the funniest comedy, and Wall-E the best family film.
New mum Angelina Jolie was voted the summer's sexiest babe for her role in Wanted, while Tom Cruise was the best scene stealer for his small part as a movie producer in Tropic Thunder.
