Can’t complain, but sometimes I still do.
I generally like:
Peachy keen
But am also partial to:
Do you want me to be honest, or reassuring?
“If I were any better, I’d be illegal.”
Gets a laugh every time.
I’ve also responded with “Great! In fact if things get any better I may stop contemplating suicide!”
In a realy upbeat voice:
“Drunk! Thanks for asking!”