Darabont's script had weaknesses where Koepp's had strengths, and Koepp's had weaknesses where Darabont's had strengths.
The problem was that there was too much nostalgia driving each script, and I think that it fundamentally changed the spirit of the film. If they had done Indy IV in '93, before audiences had lots of time to reminisce, they wouldn't have brought back Marion or included his son. It wouldn't have been as much of a family picture, just an action/adventure chapter. Including his family probably seemed like a natural thing to do given Indy's age.
I thought Koepp's script was lacking, and I thought Darabont's was a bit excessive. The part in City of Gods where Indy mimics the fertility idol scene in the library - I wanted to vomit. And the inclusion of his father was forced. Just because we all loved Indy's dad, and we loved the shtick between them doesn't mean that he should be included for the hell of it, to tell us that he's still alive. He should serve the action in some way. If it were a Tarantino film, I'd forgive the excess, but it's an Indy film, and they're supposed to be slick and efficient. The ultimate Indy IV script could have come out of a collaboration between Koepp and Darabont - they could have hit the middle ground. In a fourth installment that takes place so far after the OT, you need to address nostalgia, but you can't let it be the foundation for plot elements.
I also hope that if they did decide to make two more they would make them independent films. An Indy 5 that goes into Indy 6 contradicts one of the features of the franchise. It's supposed to be like a serial. A succinct section of Indy's adventures, not a saga of connected stories. That's part of all the fun - the same central character, but new supporting characters, new locations, new plots, all in the same familiar formula.
