You make some valid points, and I don't necessarily disagree with a lot of what you're saying. It's extremely hard to compare era's.
Example = Who was greater....Curtis Martin, or Jim Thorpe? (apples & oranges here?)
Do we penalize Martin for playing in a day of "modern medicine"? Do we reward Thorpe for not? Personally, I've always thought that Thorpe was regarded as GREAT because of what he did in his athletic career as a whole (college sports, baseball, football, and track). Thorpe played in about 50 games of pro football, and had 10 TD's I believe (someone correct me if I'm wrong). Martin played 3x's as many games, is 4th all-time in rushing, and he has 100 TD's.
"It really strikes me as odd that 9 out of the top 10 RB's of all time spent a big chunk of their careers in the 80's and 90's."
Well, I'm 33....and I didn't start watching football till the late 70's/early 80's.

You are probably much older, and have more of a connection to those old-timers. I DID give many of the guys you mentioned an honorable mention. My dad still says that Unitas was the best ever, but I've only seen him play in old hi-lights.
"The magnitude of great, historic plays are way amplified in the playoffs and SB, so I put alot of weight on playoff sucess."
Excellent point, however....I personally only hold QB's accountable for playoff, and Super Bowl success. QB's have their hands on the ball every play.....a RB may get 20 touches, a WR may get only 5-10.
Anyway.....it's an interesting discussion, and I appreciate your thoughts. I guess we'll have to agree to disagree about C-Mart. Although, I bet you a case of your favorite beer that he
DEFINITELY gets in the HOF.