He was #2 during Calzaghe's time. After Joe retired, Kessler was #1 until losing that status in Super Six if I'm correct.
I guess... I mean Kessler was a favorite in the Super 6, and I suppose he was considered the best by default after Joe moved up in weight. So you could say he was the best in 2008-09 until he was outclassed by Ward, but the victories he had after losing to Joe hardly earned him that status.
I cannot even comment yet about this fight because we all KNOW what we know about froch, but GGG is still an unknown quantity for what he could actually accomplish or not accomplish against the likes of Carl Froch. GGG is an emotionless and practical boxer/ puncher who could very well fold under pressure if he couldn't impose his will on a fighter than really nobody could impose their will on.. Ward mainly just outsped Froch but the cobra was dangerous the whole fight even coming on in the 10th on. GGG would have to really hurt, not buzz, but hurt the Cobra to win the fight and we've never seen Carl hurt so bad he was in serious trouble and against good 168 lb punchers. Until I see more of the khazak KO machine I can't say he'd beat Froch. I'd could get a good gaging of how triple G could do against Froch if he did a number on Sakio Bika.