Looking at your more complete list, I see a bunch of QBs who were first picked who did well, with only one or two exceptions. I see some QBs who were picked second or third who also did well. (Overall picks aren't really fair, as teams have many reasons for selecting other positions.) And I see a couple black swans, like Romo.

That's what you would expect if they were really good at their job. If they were bad at it, you'd expect more first picked QBs sucking, and more people coming out of nowhere.

Objectively measuring is impossible. Passer rating is more an indication of the quality of a team's offensive line, receivers, etc. than QB skill. It's a nice number for commentators to throw out, but it's of little use to a statistician.

I'd say maybe Pro Bowls, but again, there are other factors in play there too.