But, but... Indiana Jones is not a "regular" guy!
Dr. Jones is an archeologist, true...but his appeal, at least as played by Harrison Ford, is that he's a regular guy facing down insurmountable odds. Who would you rather see facing down the Third Reich and a whole slew of cultists---Ford's Indy, or Selleck's?
Then there's the other Q---how would the famous scene in Raiders play out, the one where the henchman brandishes a sword and Indy just shoots him? IIRC, the scene was filmed that way since Ford was, um, realllly sick. He didn't want to do a big fight sequence as originally intended, so the scene was re-written, and Indy just shoots the guy, and well...film history was made.