According to yahoo, Bengals tied with Giants for 18th best QB options in the NFL

[*ochocincos*]

It's clear many of these rankings put a lot of significance on playoff wins and stats, and that's where the Bengals and Dalton have floundered.
Personally, I put more stock into regular season performance since it's 16 games vs 1-4 games, and I also view QBs like starting pitchers in MLB...Need to have had at least a few seasons of good production before I consider you to be a good player because just like SPs, young QBs can have early success because there isn't much tape on them.

Regardless, with Dalton helping the Bengals to the playoffs in his first five seasons, that has come to be expected and keeps him above 20. Given the fact his stats have been poor and the Bengals have never won in the playoffs during his tenure, that's also why Dalton continues to hover around the middle while being considered to have a low ceiling. Since the Bengals did not make the playoffs last year, he's dropped a significant amount because he was expected to take the team to the playoffs.

If we want to see Dalton climb the rankings, the Bengals need to make the playoffs again and ideally win 1+ games with Dalton at the helm... and/or some of the younger more "hopeful" QBs like Carr, Mariota, Winston, Prescott follow the same route of rarely making/winning playoff games.