Tom Sellack is a matinee idol heartthrob. Harrison Ford … is not. He’s a good looking man but he doesn’t look or really carry himself like a Movie Star. Sellack has the kind of looks that would have gotten him this part back in the 30’s. Ford looks and carries himself like a carpenter who still can’t quite believe his luck.
Ford’s Professor Jones is not a sexy Bond-substitue. He’s a nerd who really cares about antiques and history. He’s not into the glamour or excitement. He’s not an art thief. He really does want to take that priceless cross and put it in a museum where it can studied in safety.
Ford’s Indy subverts our expectations of what The Hero should be like. Sellack is charming and studly - and also exactly what we’ve come to expect our Movie Heroes to be. When Ford gets the girl, it’s because she sees his true self behind his everyman appeal. When Sellack gets the girl - well, you know why he gets the girl. It’s the same reason he gets all the girls. Big whoop.
Everyone in the audience dreams of being Indy at the end of that movie. Ford makes it easier to imagine ourselves in that role. Sellack, by not being an everyman, makes it harder.