Let's just list out the great-to-good QBs in the league: Peyton, AGod, Big Ben, Drew Brees, Eli, Philip Rivers, Matt Ryan, Flacco, Andrew Luck, SCAM, and Romo. I'd put RGIII, Stafford, Bradford, and Dalton in that next tier.
Looking at that list, we have 12 1st rounders, 2 2nd rounders (33rd overall and 35th overall), and Romo as the edge case.
Obviously we already mentioned Tom, Russell, and Kaepernick as late QBs that fell into great rosters.
This isn't looking within the last five years. This is looking over the last 15 years and the significant QBs in this league. Even including Tom, Russell, and Kaep, that is:
12 1st rounders
3 2nd rounders (33rd overall (1st), 35th overall (3rd), 36th overall (4th))
1 3rd rounder (75th overall (9th))
1 5th rounder
1 unsigned rookie
I'm not saying that QBs will make your roster go from good to great. I'm saying that as long as your offensive line isn't a complete and total shit show, take advantage of the situation you're in and take the QB you believe can turn your franchise around. You can keep waiting and waiting with guys like Jackson and McGloin and get absolutely nowhere fast. Having an answer at QB gives you significant bit of leeway when building a roster.
Then again, you could be the Vikings and draft Ponder as the rest of the league laughs at you.