Lets look at the 1st rounders of a couple GM's that are usually considered among the best. Ted Thompson, Ozzie Newsome and Bill Belicheck. Those guys are generally in the list of top 5 GM's.
Thompsons last 6 first round picks:
2010 23
Bryan Bulaga Offensive tackle Iowa - If healthy a top 5 RT
2011 32
Derek Sherrod Offensive tackle Mississippi State - Bust partially due to injury his rookie season.
2012 28
Nick Perry Defensive end Southern California - Was off to a good start this year but his previous 3 were lackluster and injury plagued
2013 26
Datone Jones Defensive end UCLA - Three sacks in his first 2 years 6 games, lackluster start.
2014 21
Ha Ha Clinton-Dix Safety Alabama - Slow start to rookie year, didn't start till 7th game. Up and down production mediocre rookie campaign.
2015 30
Damarious Randall Safety Arizona State - Off to a good start, getting snaps as slot corner.
Six picks for the Packers 1 good player (Bulaga), Dix and Randall off to good early starts. Jones not gonna call him a bust but he hasn't validated a 1st round pick yet. Perry had 3 bad years and was decent this year before getting hurt again. Sherrod a bust. So 1 good, 2 promising 1 injury prone and 2 bad/bust. Looks like 50% have worked out.
2009 23
Michael Oher Offensive tackle Ole Miss - Is on his 3rd or 4th team in the last 2 years. Bust
2010 —
No pick — The Ravens traded their 2010 first-round pick to the
Denver Broncos in exchange for the Broncos' 2010 second-round (43rd overall), third-round (70th overall), and fourth-round (114th overall) selections.
2011 27
Jimmy Smith Cornerback Colorado - Watching the last gameday thread for the Ravens on FF every Ravens fan was screaming that he sucked and sucked bad. Bust
2012 —
No pick — The Ravens traded their 2012 first-round pick to the
Minnesota Vikings in exchange for the Vikings' 2012 second-round (35th overall), and fourth-round (98th overall) selections.
2013 32
Matt Elam Safety Florida - First two years were lackluster and disappointing. This year IR'd early missed whole season. Bust?
2014 17
C. J. Mosley Linebacker Alabama 1-time Pro-Bowler, first Ravens rookie to reach the Pro Bowl. Stud
2015 26
Breshad Perriman Wide receiver UCF - Hasn't played this year due to injury on a team desperate for WR help.
So last 5 Picks 1 All Pro, 1 undecided and 3 busts. Looks like 40% and could go down with Perriman.
Bill Belicheck..... Screw this guy we all hate these cheaters. On a side note I think their last bad first round pick was Laurence Maroney in 2006 he has a great track record, when they keep their firsts. But looking at Newsome and Thompson, two of the better GM's in the NFL call it 4 of 10 are good or better 1 undecided and 6 busts or injury prone. Forty percent while a random number chosen by somebody sounds about right for first round picks. There was another stat I found when looking at 1st round pick history. In the last 30 years only 4 QB's taken in the top 5 of the draft have won Super Bowls. Peyton, Eli, Elway and Aikman. A couple others were in the 6-10 range. First round picks aren't nearly the lock people seem to think they are.