Personally I rank QBs based on how well they can win from the pocket. Because the pocket is where the protection is. If you make your living outside the pocket at this level you're on borrowed time. Certainly you are unlikely to make it to that hallowed ground of late 30s QBs who have full mastery of the position from many years of seasoning. I think being able to win from the pocket is a base level requirement for that to be an expectation.
And by extension how many can win from the pocket without a run game. When a defense is dropping its ILBs and pinning their ears back. The answer is not many of these guys.
There's a whole bunch of QBs nowadays who require run games or who are their run games. The latter can be quite good too, but they don't generally last. It's a subjective thing to rank QBs. Nobody has all the answers. But I think the pros should start with that question of who wins from the pocket and can do it in big games with no run support. Which means Stafford is up there on my list.
Of course father time is undefeated. And Stafford has hard miles. So I do think the Rams will be taking a QB earlier vice later in one of the next couple drafts, and that may irritate Stafford but the team has to insulate themselves against him falling off a cliff.