From both the trailer and gameplay shown at E3 it appears that Capcom's trying to market Dead Rising 3 as a more serious survival horror game in stark comparison to the original Dead Rising and Dead Rising 2. This article on gamespot confirms that Capcom is changing the franchise drastically from its dark humoured roots.
"Capcom Vancouver presented Dead Rising 3 behind closed doors, walking us through the demonstration that debuted during the Microsoft press conference while answering questions about the direction that they've taken. The changes that you can see in images were not a fluke. Capcom is pointedly trying to appeal to a wider audience in this latest iteration, saying it's going after the Call of Duty player. Gone is the cartoonish visual design, replaced by a more "realistic" interpretation of a viral apocalypse. That change is part of the maturation. By shifting the art style, the combat can be "more visceral" than in previous versions, with "real gore."
Another notable shift is to the pacing. The urgency that defined Dead Rising has been turned off in the demo we were shown. Time created "extreme pressure" in the original games, and Capcom wants the zombies to be your biggest threat this time around. In Dead Rising 2, you now run around broken-down neighborhoods, killing zombies in horrific ways without real motivation to push forward."
So they seemed to have taken away time urgency, fun, and color from the series.