No way do they rank with Steelers/Bears/Ravens
I would totally agree with that, except for the fact that the Seahawks are doing it in the current NFL rules environment, which is offense-weighted to say the least.
You hear of guys like Walter Payton, Jerry Rice or Jim Brown?
How you define greatest ever is going to largely depend on how one views the importance of various positions to the game. Rice will never make a dent in any serious discussion about the greatest NFL player ever simply because it's nearly impossible to argue that WR is the most important position in the sport. Payton and Brown are really serious contenders, but again, whether you go with a Brown or a Montana will likely have more to do with how one views their positions than anything else. Nowadays it's hard to imagine the role a dominant running back played in the early days of the sport. Same goes for defense. The LT camp is there because they feel defense is more important than offense, LB is the most important defender, and LT was the best LB ever.