I think that it's not that Vicksburg has a relative lack of drama compared to, say, Gettysburg... I think it's a perceived lack of drama, because there were certainly plenty of exciting "scenes." The fact that the outcome appears so lopsided in favor of the Union in retrospect really underplays the difficulty of the feat and how hard the Union had to work to get there. Gettysburg has a solid place in our culture (rightly or wrongly-- the latter in my opinion) as the "moment" where it all could have gone differently, so it's easy to sell a producer on the drama. The would-be Vicksburg filmmaker has to work harder and do more to convince a production company-- but I think it would amply repay the effort. (If done well, of course.)
For instance, on the surface, the story on the rivers at Vicksburg appears to be one of total Union dominance, right? But... look closer. When I was choosing the most dramatic/exciting things to possibly cover in a potential talk at our CWT Vicksburg trip, my mind naturally turned to the USS Cairo and the dash of the CSS Arkansas... both Confederate successes. I thought that remarkable. (And I was reminded of Ed Bearss' book, Rebel Victory at Vicksburg. Maybe that title would get a producer's attention?)