To me, SR2 was the most fun I had in the Saints Row series.
SR3 was kind of meh, the only serious moment I can remember is right at the end if you pick the wrong/bad end choice. And if you pick the good end choice, you're greeted with more sillyness...
SR3 certainly was fun, but it was more... I don't know, forced?
And seriously, where the forget is a proper funeral for Johnny Gat? Where are my dramatic death scenes goddamnit!1!!11