I'll take a crack at this. Me personally I'm going to omit guys like Favre, Warner and McNair. They played in the 2000s but there's too much overlap with the 90s when talking about their careers imo
Big four are obviously Brady, Peyton, Brees and Rodgers, no ones going to argue there. From that early era you can't forget about McNabb, he was legitimately seen as a Top 5 qb and as high as 3 sometimes in his heydey. Of the 04 class I really think the only guy that makes it for sure is Big Ben. Rivers and Eli just never threatened that upper eschelon when they played despite good years here and there. I personally value peak performance and how you're viewed amongst your peers over longevity, counting stats and team achievements so that's my reasoning here
Feel like Matt Ryan and Stafford make the list with Ryan's case being better than Stafford's. They're both better players than guys like Eli but were also seen in the second tier when they played. I'd put Russell Wilson in the same category too, in that second tier but several years of high play and seen as one of the better qbs of his generation
Cam's is an interesting case; he doesn't have the longevity and his base stats betray his impact as a dual threat, but he was such a floor raiser when he played and his peak was higher then several guys seen as above him. I'd put him on the lower end of the 15. Luck's a similar case but I'm not sure if he'll be able to make this list. Romo I feel like has been done dirty by his association with the Cowboys but he was a really good QB. He's another one though I'm not sure about making the cut
Among the newer generation Mahomes and Lamar are locks, and I think Josh Allen has shown enough at this point to be on this list as well. Burrow is interesting to me, he might squeak in because he's seen as in the first tier of his generation in ways that many of the people mentioned above weren't with theirs. I don't think anyone else from this current generation has shown enough to make a list like this