All I want is a GTA that's less personal. VCS and before didn't dig too deep into the protagonist, I mean you didn't get to learn much about the protagonist in the older ones and that's what made it more fun - wondering what could've been. Too much detail on characters now, not saying I hate it though.
As for dark or not, I'd say no. It's a game, not a movie! The main reason IV's story wasn't terrible as a whole was because Niko was a badass.