Well, I couldn't say Bruschi or London Fletcher, obviously.
Thomas, Bruschi, and Fletcher are all decent middle linebackers. Thomas got to a few Pro Bowls and Bruschi got a few Super Bowl rings and lots of "good loving" by the media.
But, as football players, none of them hold a candle to Ray Lewis in his prime, for example.
Harry Carson just happened to be an above average LB on a great defense in New York. How many Super Bowls did Carson carry his team to victory in? How many teams game planned around Harry Carson and didn't worry about LT or Carl Banks, etc.? Brad Van Pelt was an above average LB too.
With Carson, I just think if he played for a bad team like the Cardinals, Bucs, or Falcons of the day, very few fans would remember him at all.