The producers of the Buffy the Vampire Slayer movie reboot wanted Whedon on board, say insiders.
The announcement that a reboot of the original Buffy movie was in the works, without creator Joss Whedon's involvement, was almost more than some fans could bear. According to insider sources, however, Whedon could have worked on the reboot, but chose not to.
Whedon responded to the announcement of the reboot last week, and seemed to be taken by surprise, but if the rumors are to be believed, he was well aware that it was a possibility. Sources say that producers Fran Rubel Kazui and her husband Kaz Kazui approached Whedon to work on the film before they talked to anyone else, but he wanted to work on other projects - like the upcoming Avengers movie - instead. It was only after Whedon turned the project down that the Kazuis started looking for another writer, eventually going with neophyte screenwriter Whit Anderson, whose take on the story was strong enough to catch their attention.
If the rumors are true, we can only speculate on what Whedon's motives might have been for turning the project down. You might make the case that Whedon was done with the franchise but his involvement with the canonical spin-off comics shows that he's still got plenty of Buffy stories left in him.
A more compelling argument might be that Whedon already has rebooted the movie once, and turned it into a very successful TV show. It's quite possible that the prospect of dropping most of the characters and stories he'd developed to reboot a version of the story he wasn't very happy with in the first place didn't sound too appealing, and certainly wasn't going to win out over the chance to work on the Avengers movie.
Source: Heat Vision Blog