You're certainly right about individual interpretations of "fun" films. I wouldn't categorize those based on just humor, however. Less tangible components include (for me), the pacing and exuberance of the story and the way (some or all of) the actors run with what they have. Another intangible is connection with the basic storyline. In contrast to Van Helsing, a film with recognizable issues that still is "fun" in my estimation (sometimes only when viewed with a less critical audience, like children or grandchildren), is The League of Extraordinary Gentlemen, a film I really wanted to like, but found bereft of both tangible and intangible components.

... Reed