You think that it should essentially be a joke just because it's a videogame? I strongly disagree. Games can be a powerful storytelling medium, and I think The Dark Tower could make a fantastic, serious, adult RPG or action game. Something along the lines of BioShock or even Red Dead Redemption would be wonderful. If they were going to make a 'funny' fighting game as you suggest, I'd rather they not make one at all.
The thing that interests me most about the recent revelation that they're actually planning a Dark Tower game is the idea that it will draw upon elements from the books that were not used in the films. Perhaps the game(s) will have sections involving related King books like 'Salem's Lot, The Stand etc? A prequel side-story where you play as Callahan during the vampire infestation could make for terrific downloadable content...