It goes without saying that the more stuff there is in a game, the less polished it can be, and Rockstar games are remarkably polished despite that obstacle. Add to that some very powerful escapism, accessibility, great production values and it's easy to see why they are so liked and why they're remarkable titles whether you like them or not (and I'm not a superfan of Rockstar games, honestly).
Considering people on this forum are willing to excuse role-playing games for being unpolished and buggy as hell, I can understand why they can excuse Grand Theft Auto for not having perfect shooting/driving mechanics.
I'm sure you can make some compelling argument about why Dragon Age II is good, but you can hardly use that reasoning since it's a game with a very focused, almost narrow scope in design and content. Then again, I never mentioned Dragon Age II in the first place, so I'm not the most indicated to reply on that point.