Goldwater was a Senator and a (real) presidential candidate, Paul never got taken seriously, now he is old.
If Ron Paul wasn't "taken seriously", there wouldn't be a Rand Paul successfully running for the Senate. Much/most of Rand's campaign contributions came from his dad's fans before anyone even knew what Rand Paul was really about, other than being his father's son.
Ron Paul may never become president, but I would not underestimate his effect on today's politics.