Recently I've been thinking about Sandman in SM3 and how much they messed his story up. It seems to me they wanted to replicate the formula of the other movies, so they gave him this drawn-out backstory with his sick daughter, as well as making him Uncle Ben's real killer to tie the 3rd movie back to the origin, both of which were unnecessary and dragged the movie down. The part with his daughter never even pays off (I guess she's still gonna die). Sandman's not a complicated guy. He doesn't need all this stuff added on to make him more "interesting" especially when he's sharing the movie with two other bad guys.
Here's an example of how they could have approached his character (and yes, a lot of this is right out of SSM): Flint Marko is a run-of-the-mill petty crook. An action scene in the opening shows him getting his ass kicked by Spidey, and we quickly learn that this isn't the first time (Spidey even recognizes him), so the guy's kind of got a grudge. Then he stumbles on to these super-powers (either in an experiment or a random accident like in the film). With this new upgrade, he suddenly realizes he can steal anything with ease, while finally wiping the floor with Spidey to pay him back for the repeated humiliation.
That's it. No tragic family, no Uncle Ben connection. This is all Sandman needed. They could even keep all the same fights. Dropping all the other stuff would have left more precious time for the movie's other myriad subplots and motivations.