It might be interesting to chart that.
As far as I remember, crowds were really unpleasant in late '05/early '06. Very gradually, as the year went on, there was an acceptance/grudging respect in a lot of buildings. I think Edge deserves credit as a heel there.
Feuding with Michaels in early 2007 (instead of Hunter) elevated Cena's work and standing to a degree, but HBK was much more popular among hardcores/adult males, so that unfortunately knocked him back to square one.