In modern history, acceptance speeches by incumbent presidents have been largely unmemorable.

The biggest exception was Franklin D. Roosevelt's, as he ran for a second term in 1936. In that speech, delivered in Philadelphia, FDR uttered one of his most stirring passages ever: "There is a mysterious cycle in human events. To some generations much is given. Of other generations much is expected. This generation of Americans has a rendezvous with destiny."
 
Bill Clinton also had a memorable line in his second-term acceptance speech: "build that bridge to the 21st century."