... the Doom 3 engine is just perfect for a Marathon recreation ;-) It already has a great system for recreating terminals and managing goals, data, maps etc., already has a similar feel as far as player movement and physics, and sure as hell can recreate the kind of grubby industrial environment that I personally associate with Marathon.
And while I agree with Jorge that all of the graphical buzzwords and features in the world don't make for a good game (Doom 3 proves that), but used correctly they can make a great game even better (Half Life 2 proves that). If you manage to recreate the atmosphere, the pace, the narrative flow, and the overall nebulous intangible gameplay goodness that was Marathon using a next-gen engine like Unreal or the Doom 3 engine, how could that be a bad thing? And personally, I wouldn't necessarily want the old games or scenarios shoehorned into a new engine; that seems pointless and almost inapproriate to me. I would however love to see a new scenario written from the ground up with the idea of utilizing the new technology to tell a story in a way that wouldn't be possible with the older engines. An original game in the Marathon universe, continuing or expanding on the original storyline, with the sort of cinematic sweep that the new engines can provide... that would be swell : )
That being said, to my mind the real problem with these new engines is that in order to exploit their new capabilities, you need to create a ton of content, and that content is becoming more complex. Once upon a time a bunch of pixel-art textures of a fixed size, shape and palette was\s all you needed to dress up a few simple polygons to create an environment. Now, textures have to be high resolution and very detailed, and for every texture you need bump maps, glow maps, environment maps, etc. I never thought I'd see the phrase "shader networks' outside of high-end 3D tools. You need high quality 3D models/brushes just for the levels and environments, not to mention the amount of modeling, rigging, and animation skill required to make a halfway believable character. The editors themselves are very complex, with literally thousands of parameters that can be set for any given item. Even the friendliest (like UnrealEd) are orders of magnitude more complex than Forge, and just as buggy.
Half Life 2 ships with a version of SoftImage as an editing tool, Doom 3 uses Maya and 3DS Max to create models and static meshes, Halo uses Max for models and meshes... these are tools that used to be used for high end Industrial Design and movie making, and now they're needed to make a reasonably advanced game!
Every Marathon scenario seems to have run into trouble creating content. Getting maps done is a big chore. Getting textures made is a big chore. Getting sprites/models made is a huge chore. For every Eternal or Rubicon that manages to muster the resources and resolve to tackle that big of a task, there are dozens that get set aside. And the new engines make this an even bigger task, requiring more and better content from more and more skilled content creators.
Once I'm unemployed I might just take a swing at a small scenario or level using the Doom 3 engine, but I can't imagine tackling that kind of an endeavor while trying to hold down a job ;-)
