I think Vick has to be the most overrated QUARTERBACK in the NFL, however not as a playmaker...he is way too inaccurate to be an elite QB. I also think Mcnabb is a little overrated as he is not the most accurate QB either. I think Westbrook is underrated for that team.
I always thought John Lynch was a little overrated until I saw him with Denver this year, he tore it up.
Plaxico Burress is made of glass and plays scared. Jevon Kearse has never been great since his seasons with the Titans, injured or not.
Another player that may be overrated is Ed Reed, while he has had great seasons, he really struggled last year and perhaps the Ravens defense was protecting him, however they just changed to a 4-3 from a 3-4, so maybe he just has to adjust.
Edit: I think Chad Pennington is overrated as well, he has a noodle for an arm.
Lastly, no Cowboy is overrated, and if anything they are underrated and the only reason they don't win is because there is a league wide conspiracy against them...