Two ideas, basically.
The first one: "Indiana Jones and the Infernal Machine", only with next generation graphics and features. That baby was definitely the best Indy game of all time (yes, I even prefer it to "Fate of Atlantis", and I truly think it was the only Indy story that was worth the first three films... damn, why didn't they use THAT for "Indy IV"
) and having it remade would just be one Hell of a move.
The second one: a brand new graphical adventure, similar to "Fate of Atlantis", but with ultra high quality pre-rendered graphics in the style of Benoit Sokal games (Syberia, Paradise, and so on).
If done well - current 3D engines should be capable of moving an almost photorealistic environment with not too much trouble, think of games such as Gears Of War or Uncharted - they could also integrate the graphical adventure with some big 3D action sequences, quick time events or things like that, just to bring in the feel of a real, spectacular Indiana Jones adventure movie on your PC.
These are my 2 cents.