Arnold got fired from the Apprentice so Trump is greater.
Arnold is a gifted relationship-builder, social climber, innovator (bodybuilding, tough man roles - all of which he pioneered) and all around larger-than-life superhero character on and off the screen.
But he's not Presidential material and never will be. On stage with 9 seasoned Republicans 2 years ago, he'd have been crushed rhetorically and intellectually. It's one thing to impress the hell out of an audience when you're a guest speaker or signing autographs; it's another to convince 40-50 million people to cast their vote for you after two years of endless campaigning, media assassination initiatives across every major network and news outlet, fighting off 9+ Republican candidates, and beating the most formidable Democrat contender available who has 30+ experience in politics, 8 of them in the White House.
Trump is a phenomenon that only comes along once every 100 years because of what he did in 2016. Prior to that, I'd have said he was just a sharp businessman who rebuilt himself after badly-timed investments and credit-based spending that didn't pan out, and a great entertainer.