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.

I'd say The Longest Journey/Dreamfall. Especially Dreamfall, it practically was a movie anyways. Sometimes I just want to experience the story without having to "play" the game.

Games to movies? None, absolutely none. Taking a story made for a medium when you have huge resources of time, have to concentrate on gameplay, and have more direct immersion, and adapting it to a medium when you have a couple of hours, conservation of detail is king, and a passive experience? Disaster everytime.
Movies to games, although usually bad, don't HAVE to be. Although most of the good candidates are already adapted. Princess Mononoke perhaps? Medocire movie, but the Ben Affleck vehicle 'Paycheck' could make a basis for a sweet adventure game.

Full Throttle.
The game WAS a movie... Now let's just make a live action version.

There is a Fallout MMO in the works by Interplay. They haven't sold all the rights to Bethesda, but they have to finish and publish the game on time, or Bethesda takes everything. They still have something around 4 years.
FEAR
I think the game was originally supposed to be a sequel/prequel (can't remember) to a movie already in production when the game came out.

Its clearly opinion because its my opinion posted on a discussion board.. I'm supposed to add a disclaimer to my post because some people take things two seriously and turn into junior jobsworths?? Pretty much everything on thee boards is opinion.
Doom the game has zero plot, hitman is generic in its characters, plot and setting. While both COULD be made into movies, whats the point... it'd be like making a painting based on a photo of the mona lisa.
PS/ You have terrible taste in movies.
Metacritic: Doom: 34%, Hitman 35%.

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In an effort to be more positive, another game i think would make a good movie is Psychonauts. Not live action of course, but it'd make a great pixar-style animation. Heck, they could basically just cut together all the cutscenes ;-)
Although i think one thing to bear in mind is that great games don't necessarily make great movies, or visa versa. Halo is a cool game, but i don't see it's movie being anything other than generic sci-fi. Chrono trigger is one of my fave games of all time.. wouldn't work as a movie. Same goes for Farcry, Half Life, GTA, etc..
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Strange noone has said anything about Silent Hill the move yet, it is the most successfull movie adaptaion of a game. Christphe Gans, the director, has in several interviews said that what he wanted was to try to catch the feeling of playing a game more then re-enacting a game story line, and I think he managed it very well. It goes without saying that he is a gamer himself ,and that SH is one of his favorite game series, the reason he wanted to do the project. Offcourse most movie critics didnt understand it at all and sleted it, something to do about not playing? But if you havent seen it, try it. It can be a little experimental in places, but it is all part of trying to recreate the experience.
When it comes to what game that would make a good movie, I would go for Half-life or Deus Ex., but a Primal or Soul Reaver movie could be interesting - if well made.

A Grim Fandango movie, with state-of-the-art computer animation would be cool.

Thief done right, by like Jackson, Ridley Scott or someone I think that would work - Christopher Nolan (don't just look at The Dark Knight, but The Prestige, with the cloning/Tesla stuff and atmospherics of that film.) I think Nolan could do a tremendous job. He really seems to have his heart and mind in the right places and priorities for what makes a film good. Thief would definitely make a great trilogy then. There's a lot cool elements in those stories that would make a unique film. Clive Owen might be good too for it. Not too sure though, I would have to play the games again.

I would like to see Threads movie as a game. Why not also Shaun of the Dead.

The problem with movie to game scenarios is that movies usually last around 2 hours, games start around 5 hours. This usually result in the movie-plot being filled with generic looking spaces in between.
There is also very often the issue of ip's that need to be respected and the quick development time that is demanded to have the game release at the time of the movie release.
Games to movies is easier, but also not without its difficulties. First off game storylines last longer than those of the average movie. Secondly, a proper movie based on a game will cost huge amounts of money. To be profitable they need to attract more people than those playing the game. This often leads to dumbing down of content at best, but in some cases they cut about everything except the title and some of the characters.
Of course there are games that should never ever be turned into movies.
Anything with Mario in it, what where they thinking back then, or any other platformer character for that matter. Anything that had little story to begin with is also a bad choice.
As a final note. An animated film based on a game is preferable over a live action one imo.

Assuming that moving to books instead of movies isn't too far of a jump for this thread, I would love to see Jack Campbell's "The Lost Fleet" series (Dauntless, Fearless, etc.) turned into a game(s). The fictional universe would plug perfectly into a space sim.

An interesting thought just occurred to me. It'd be nice to see a sequel to the movie TRON. The thing is, the game TRON 2.0 already is a sequel to the movie, and has a great and very cinematic storyline. If they based the movie on that, the TRON franchise would have come full circle.