It's got to be the ridiculously inaccurate Street Fighter: The Movie, starring Jean-Claude Van Damme, Raul Julia (in his last role), and Kylie Minogue. It forsook a ton of backstory material that would actually have made it a half-decent popcorn flick, and came up with a load of nonsense, instead.
Capcom actually believes that this was a popular film (and appears to have missed the fact that it actually has an internet following because it is *absolutely terrible*), and in recent years licensed out an unrelated Chun-Li focussed "follow-up" to try to capitalise on this. It didn't work (it didn't help that they cast that whiny girl from Smallville as Chun-Li).
However, nothing will ever be able to stand up to the juxtaposition of Raul Julia's genuinely excellent depiction of M. Bison, the weekend-morning-cartoon style of some of the supporting cast* (especially Zangeif, who gets some of the most hilarious moments in the film, such as the fantastic "CHANGE THE CHANNEL!!" bit), the completely random soundtrack (I have the CD because it has one or two worthwhile tracks, such as the one by Chage & Aska, but seriously, it is VERY random), Jean-Claude Van Damme's hilariously misdelivered, non-American-sounding lines for the all-American Colonel Guile, and the goofy cast freeze-frame at the very end, which was made to match the games.
*(They actually did go on to license such a cartoon series, which was a direct follow-on from the movie's storyline, as the video release of the film, as well as the much later DVD release, features an added post-credits segment which hints at a sequel.)
I absolutely love it, even though I'm fully aware that it is a bad movie. The thing is, though, that it's so bad it's good.