I've given this a lot of thought, and I think "doing it right" is impossible.
The problem with DOTT is that there is a massive amount of going back and forth between the exact same locations. The story is brilliant for a game, but I don't think it would work in the context of a movie. All of the action would have to be completely rewritten, in order to minimize tedium (and confusion) for the viewer. That said, it might make a good movie, but mostly for people who have never played the game.
Looking at it from that angle, I think Zak McKracken has a lot more potential to make a movie that would satisfy both old fans and newcomers.