Cutler and Palmer are red herrings. Cutler got traded to one of the worst offenses in the league. His leading receivers were Johnny Knox and Devin Hester, and his line was the worst in pass protection in the league.
Cutler's YPA in Chicago has been about the same as it was in Denver. The difference is that he's no longer throwing the ball 600+ times per season. He wasn't a great QB in Denver. Even in his 4500+ yard season he averaged just 7.35 YPA, which incidentally is about what he has averaged over the last two years in Chicago.
Palmer was great until his knee got shredded, and hasn't been the same player since.
It's a big myth that Palmer was a great QB in Cincy. He wasn't. Palmer never had a season above 8.0 YPA until
after he ripped up his knee. He was never a great quarterback. He was a guy, like Cutler in Denver or Stafford last year, that people overrated because they didn't focus on the right stats. A slightly above average starting quarterback can look like a great quarterback to you if you just look at things like total yards, fantasy points, and passing TDs. The problem with those stats is that they don't necessarily reflect the quality of performance. To a large degree, they are measures of opportunity, not performance. TDs are flukey and fluctuate wildly. QBs like Brady and Manning have had +/- swings as big as 20 TDs from one season to the next. The same thing can happen on a smaller scale with lesser QBs like Stafford, Palmer, and Cutler. They can fluke their way to a season that's +10-15 TDs over their realistic expected yield, and people will suddenly start valuing them as if that's the norm. If the analysts had looked at YPA, they would have realized that those players were never playing at an elite level.
Stafford is the poster boy for this. It's widely assumed that he played at an elite level last year, but in reality he was a high TD/high attempts guy with a mediocre YPA. Brees, Brady, Rodgers, Roethlisberger, Rivers, Newton, Eli, Vick, Palmer, and Schaub all had a higher YPA. They just didn't have the benefit of throwing it 663 times with Calvin Johnson as a red zone option.
Ryan is the closest thing to Stafford this year. He hasn't suddenly become a better player. His 7.44 YPA average is just a shade above his 7.38 from last year. In real life NFL terms, he's the same fringe top 10 QB he has always been. The reason perception of his value has changed is because he's throwing the ball more (which is purely a matter of opportunity) and scoring more TDs (which is probably just a result of variance breaking in his favor). He's on pace for 629 pass attempts, which would be a career high and would have ranked third among all QBs last year. He's on pace for 37 passing TDs, which is well above his career average. Basically, the stars are aligning and he's having "that year" right now, and he's STILL well behind the QBs who are actually passing at an elite level, like Rodgers and Griffin.
A QB can really only reach that OMG level when he not only becomes a high attempts guy, but also a high YPA guy. That's what has allowed Brees, Brady, Peyton, and Rodgers to have some of the seasons they've had. The good news for Ryan is that he could still reach that level (Peyton and Brady were not high YPA guys early in their careers either). The bad news is that there's really no reason to assume that he will. He has shown minimal signs of progress since his rookie year.
I'd value him right now about how I would have last year. As a top 6-10 guy who can give you weak top 5 numbers when everything clicks. In terms of value per cost, I would rather have a Romo, Eli, or Roethlisberger three or four rounds later. They are all better NFL QBs than Ryan and they have similar career FF outlooks, although they are all older. I would also rather have Luck given his draft pedigree, although that one is based on a leap of faith, and not on any statistics. Luck's YPA has been completely pedestrian this year.
Basically, Ryan is an overrated dynasty asset right now because people just look at the total points and not how he's getting there. I would much rather have a high YPA QB who isn't throwing the ball as much, knowing that he has a greater upside in the event that he gets more opportunities. Ryan is not a bad player, but he's closer to Rivers/Cutler/Roethlisberger/Romo than he is to Rodgers.