Renderking Fisk said:
Darker and rougher the better,
Only within reason, though. Dark is okay, but Indiana Jones films have always been light-hearted at their core. Even "Raiders Of The Lost Ark," which we seem to be using as a model for the ideal Indy film, has plenty of humorous moments. Yes, he was a dark, brooding figure during the opening sequence, but as soon as that boulder starts chasing him, he becomes human-- we see the fear in his eyes, and we know he's not a Clint Eastwood type. Then there's the exchange about Reggie the snake to help lighten the mood a little more ("Show a little backbone!"), and further making Indy seem real because of his fears. The rest of the movie was sprinkled with humorous lines and situatins that served to both lighten the mood and prevent Indy from becoming a superhero.
"Temple of Doom" was dark in some respects, with sacrificial altars and whatnot, but Short Round and Willy kept things light.
"Last Crusade" was arguably the lightest of the three films, and I don't think it suffered as a result. If anything, I think it's humor worked considerably better than TOD's (for me, Henry was better than Short Round and Willie combined.)
So anyway, getting back to the topic-- I think Indy 4 will do fine if it follows in the footsteps of the others. Dark moments, with enough humor to keep it entertaining.