I have linked to an article from the National Football Post which analyzed the draft histories of all NFL teams from 1993 to 2006. This article measured the success of each teams draft by whether the player drafted became a five year starter or not. He did not necessarily have to start all five years with the team that drafted him as this measures the ability of the team to find, draft, and develop talent.
The Lions were pretty bad across the board, but especially so with the 14-40 picks and 87-149 picks. Overall, though, they produced fewer than the expected number of five-year starters in five of the seven Value Groups.
The average number of five year starters drafted was twenty-six.
I hope this trend is turning around under Mayhew. Only time will tell. I think it is, but then I am a bloody optimist.
Oh, and if anyone wonders why I did not put this up as a FanShot does not visit this site very often.
NEW:I posted the following in a comment and thought it should be added into this Post.
By the criteria the study used, number of five year NFL starters from the draft, the Lions finished dead last in the time period 1993 to 2006. Seventeen  5yr starters versus a league average of twenty-six  and a league best [Packers and Steelers] of thirty-five .
I agree with DLions. It was not the position/type of player drafted, it was the quality of the players drafted that the Lions completely failed at. The Lions failed at O Linemen [Stockar McDougle, Aaron Gibson, Juan Roque], LBs [Teddy Lehman, Boss Bailey, Barret Green, Matt Russell, Reggie Brown, Antonio London], D Linemen [Kalimba Edwards, Shane Bonham], DBs [Van Malone, Ryan Stewart, Kevin Abrams, Terry Fair, Stanley Wilson, Daniel Bullocks], not to mention the skill positions of WR [Rogers, Mike Williams, Germane Crowell], RB [Artose Pinner, Kevin Jones, Brian Calhoun, Reuben Droughns], and QB [Orlovsky, Batch, McMahon].
All of the guys I listed except for four [Orlovsky, McMahon, Pinner, and Russell] were picked in the third round or earlier. The later guys are even worse.
Guys not on this list that are considered successes by the standards of the study are Harrington, Ernie Sims, and Chris Claiborne.
That is one big, ugly batch of fail.