I guess I'm just thinking of QB's that weren't "the best" in the draft, but they end up being very good.
Romo, Flacco, Rodgers, Kirk Cousins, Drew Brees, Brady, Wilson, Andy Dalton, Derek Carr, Dak..granted a couple of those were in the first round (Flacco/Rodgers). Kaep to a certain extent as well. I'm just looking at current NFL QB's and not going back in time to QBs that are now retired, though Romo is almost there haha.