He was DOMINANT from 11-13, and you could probably throw his '08 and '10 season in there too, at least as far as being a top-10 WR numbers wise....he never had a BAD season, and was a 3-time All Pro.
I tend to think of HoFers as a player who was among the top 3 to 5 at his position for a 5 years....ideally 5 years consecutively, but I think that from 08 on, if you asked anyone what WR they would want, Johnson would have been one of the first 3 names mentioned, if not THE first.
It boggles my mind that people will be against Calvin Johnson, but favor players who had long, merely-good careers - it's as if they don't want GREATNESS, they want compilers, in the HoF.
Looking at every players' first 9 yrs, Calvin Johnson ranks 6th in receptions, 3rd in yds, and 5th in tds...and 5th in receiving yds/game. He could have played longer and padded those stats, but as it is I think it's pretty apparent that he performed at a tremendously high level during his entire career, and belongs in there with the greats.