When compared with other positions, I believe offensive tackles taken in the first round (particularly those taken in the top-20) have the lowest chance of becoming a total bust.
Offensive Tackles drafted in the 1st round over the past 14 years:
2005 - Jammal Brown (13), Alex Barron (19)
2004 - Robert Gallery (2), Shawn Andrews (16)
2003 - Jordan Gross (8), George Foster (20), Kwame Harris (26)
2002 - Mike Williams (4), Bryant McKinnie (7), Levi Jones (10), Marc Columbo (29)
2001 - Leonard Davis (2), Kenyatta Walker (14), Jeff Backus (18)
2000 - Chris Samuels (3), Stockar McDougle (20), Chris McIntosh (22)
1999 - John Tait (14), Matt Stinchcomb (18), Luke Petitgout (19), LJ Shelton (21), Aaron Gibson (27)
1998 - Kyle Turley (7), Tra Thomas (11), Mo Collins (23), Victor Riley (27)
1997 - Orlando Pace (1), Walter Jones (6), Tarik Glenn (19)
1996 - Jonathan Ogden (4), Willie Anderson (10), John Michels (27), Jamain Stephens (29), Andre Johnson (30)
1995 - Tony Boselli (2), Korey Stringer (24), Billy Milner (25), Blake Brockermeyer (29), Trezelle Jenkins (31)
1994 - Bernard Williams (14), Wayne Gandy (15), Aaron Taylor (16), Todd Steussie (19), Tre Johnson (31)
1993 - Willie Roaf (8), Lincoln Kennedy (9), Brad Hopkins (13), Ernest Dye (18), Ben Coleman (32)
1992 - Bob Whitfield (8), Ray Roberts (10), Leon Searcy (11), Eugene Chung (13), John Fina (27)
Hard to find many OTs taken in the top 20 picks of a draft who went bust, so Williams would be pretty unique if he doesn't turn things around at some point. This is part of the problem, IMO, with the current CBA. Rookies drafted highly get paid a ton of guaranteed money and have very little incentive to work and earn their paychecks. Williams made a small fortune during his brief stint in Buffalo while a player like Jason Peters can outplay him for years and still not make much more than the league minimum. Perhaps a change of scenery and a more incentive laden contract will be enough to help Mike Williams begin to live up to his potential...but he may just not care enough as he already has plenty of money to live comfortably.