Right. That was really my point. Only Warren Moon in 57-years.
Blanda was at an Otto Graham level for only a short time (comparing similar eras). Steve McNair was just getting his feet wet in Houston before the move. Even at that, was McNair ever "elite?" I don't think so. A top-10 QB at one time, sure.
Pastorini, compared to his peers, e.g. Kenny Anderson, Dan Fouts, Bob Griese, Staubach, etc., Pastorini was a scrub with his 103-161 TD-INT ratio, and career passer rating of 59.1. He gets a nod in this town in hindsight, only because he was the QB on a team that had a wicked defense (though not as good as the Steel Curtain) and a HOF running back. History has been kind to him.
Ken Stabler was already washed up when he got here, and would show up to games hungover from drinking all night at the old Shamrock Hilton the night before games (rest his soul).
Matt Schuab? I'm not going to be a revisionist; Matt was pretty damn good. He probably cracked the top-10 a couple of times, and he was certainly better than Cody Carlson, Bucky Richardson, Billy Joe Tolliver, Pastorini and Stabler.
So, yeah, Warren Moon. To have a better career than Warren Moon, Watson would need to take this town the promised land.
Actually, under the premise of "on a long enough timeline anything can happen," time is ever increasingly on our side.
(Somewhere out there is a hundred monkeys on typewriters working on Shakespeare.)