It's not memorable lines that count in debates. It's screwups.
The only memorable lines are either screwups or someone pointing out someone else's screwup.
Kerry was playing to win. Bush was playing not to lose. Hence, Kerry came off as mildly presidential and will excite his base. Bush came off as unremarkable, but didn't say anything stupid.
I say this after watching the '84 reagan-mondale foreign policy debate. Despite legend, Reagan didn't look fabulous the entire time. But he had some impressive hard-hitting lines.
"It's not memorable lines that count in debates."
Hmmm, how about these?
"Are you better off today than you were four years ago?", and
"There you go again".
-Ronald Reagan to Jimmy Carter, 1980
"I will not make age an issue in this campaign. I am not going to exploit for political purposes my opponent's youth and inexperience."
-Ronald Reagan to Walter Mondale, 1984
"Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy."
— Lloyd Bentsen to Dan Quayle, 1988