Meh. I've never been bothered by frame rate OR resolution. If a game is fun, I'll enjoy it and admittedly this whole resolution war is discernable at best.
To directly answer the question OP, it boils down to one thing - optimization. How much time is a Dev willing to put in to make it reach a certain criteria? Or, what would you need to sacrifice?
Whether or not devs have gotten lazy or games have just become too advanced is an entirely separate thread.