In my lifetime, the Clintons (one cannot, should not, deny Hilary's role in the administration). Their track record isn't spotless--NAFTA sure as hell came round to bite us in the ass--but they left a legacy that commands more respect than derision, with or without that stupid blowjob staring us all in the face.
What hurts more than anything, though, is the future that died with John F. Kennedy. I didn't get born until fourteen years after his assassination, yet I swear I miss him as much as anyone who was there to witness it.
And where can I find a biography of Teddy Roosevelt? That guy was bad to the ass.