Yep, depends so much on what he likes. Central Florida is fun because of the theme parks. (I did DisneyWorld for the first time in '03, in my late '30s... it was a blast. Riding roller coasters all day at Busch Gardens was awfully fun too.)
San Francisco is an iconic US city that everyone should see.
Utah was a good recommendation. Yosemite National Park in California is stunning too.
Hiking on the Olympic Peninsula is on my list...
A weekend of baseball games in any major league city is always fun.