Historically, QBs taken in the top 5 picks have about a 50% chance of becoming a good QB. Outside the top 5, you have about a 10-15% chance of finding one.
Breakdown of QBs and where they were selected, asterisk means they made it.
QBs taken in the top 5 1991-2015: 93 (Bledsoe*, Mirer), 94 (Shuler), 95 (McNair*, Kerry Collins), 98 (Manning*, Leaf), 99 (Couch, McNabb*, Akili Smith), 01 (Vick*), 02 (David Carr, Harrington), 03 (Palmer*), 04 (Manning*, Rivers*), 05 (Alex Smith*), 06 (Vince Young), 07 (JeMarcus Russell), 08 (Ryan*), 09 (Stafford*, Sanchez), 10 (Bradford), 11 (Newton*), 12 (Luck*, RG3), 14 (Bortles), 15 (Winston*, Mariota*)
29 QBs were taken in the top 5. 14 panned out, just under 50%.. Immediately you can see that the Browns core issue is that since 1999 they only made ONE attempt (Couch). They should set a goal of picking 4-5 QBs top 5.
QBs taken in round 1 but outside the top 5: 91 (McGwire, Marinovich), 92 (Klinger, Maddox, Brown), 94 (Dilfer), 97 (Druckenmiller), 99 (Culpepper*, McNown), 00 (Pennington), 02 (Ramsey), 03 (Leftwich, Boller, Grossman), 04 (Roethlisberger*, Losman), 05 (Rodgers*, Campbell), 06 (Leinart, Cutler), 07 (Quinn), 08 (Flacco*), 09 (Freeman), 10 (Tebow), 11 (Locker, Gabbert, Ponder), 12 (Tannehill*, Weeden), 13 (Manuel), 14 (Manziel, Bridgewater)
32 QBs were taken in round 1 outside the top 5. Only 5 made it, one only made it for 5 years (Culpepper) and only 2 look to be hall of famers. The rest were worthless. The Browns have 2 picks in here (Weeden, Manziel) and of course with the long odds they missed on both.
Then if you look at rounds 2-3, there are something like 35 QBs taken and the only ones to pan out are Favre, Brees, Russell, Dalton, and Derek Carr). Again the Browns have two picks in here (Frye, Kessler) and odds would say this is bad strategy.
When you don't have a QB, and you land a top 5 pick, and you believe there is a QB that will go in the top 5, I think you have to get him. But right now I doubt the scouting community grades any QB in this draft a top 5 pick. The Browns got the #1 pick in the wrong year. That's their own fault because Wentz fell to them and they passed on him, so I guess this is karma biting the Browns for screwing up the draft last year. So Garrett should be their pick, but the way the Browns do things I wouldn't be surprised if they screwed this up as well.