It's such a pass heavy league these days that I feel sorry for the old QBs. The likes of Starr, Staubach, Unitas, Namath and Graham won't compare to the vast majority of average modern day QBs statistically so I imagine one-by-one there names will drop off the greatest of all time list.
I don't think Brady needs to win anything else. There's a reason Bradshaw isn't considered one of the greatest despite winning 4 Superbowls (not that I agree with the low ranking he usually gets in QB lists) and there's a reason Marino is considered one of the greatest despite never winning one.