I recently re-read the old Conan stories. They held up pretty darn well.
https://sites.google.com/site/skprofile00/reh-stories
The Ahnold movies didn't move the needle. The REH stories would make a great foundation, and for that matter, some of the 1970s reboot stories (Carter, Sprague de Camp, etc) would make a great path for a preplanned series of annual summer blockbusters. They'd just have to be careful with the casting, pick someone young enough and good enough, but not someone who will play hard to get later. Or maybe just intentionally recast the lead role for each movie, make that part of the publicity. There have been something like six James Bonds, for example.
I also reread Conan a year or two ago (complete Robert E. Howard on the Kindle, cheap) and it did hold up well. A few years back, I reread two Tarzan books, and sadly, they did not. Same with Doc Savage.
I have to admit I loved all of them 50 years ago.