I think that generalizing a status quo as inherently better that the other one is why i disagree the most in these discussions.
I read good stories with both characters that were single and i read good stories with characters being married as well.I donīt think one is always better that the other one.To me that is just generalization.
Good stories can be done with either status quo,but from my humble opinion unless the lore of the character is deep in the theme of family as the Fantastic Four stories,the main character status quo is not that relevant.At least to the notion that only married characters can undergone growth.
The main character being single is not by itself a indication that his stories would be worst that if the character was married.Itīs in this notion that i could not disagree more.
To make good stories i think itīs more complicated that just featuring a main character in a married status quo or a single status quo.