If you were to adapt a game, comicbook or novel into a movie, who would you cast?
Metroid
Samus Aran: Jessica Biel - Just like why I'd pick her over McGowan for Red Sonja, she's probably the one actress who can pull off the physicality of the role (both the warrior aspect, and that, as the games have shown, she's damn hot under all that armor). She's about as close as there is to an Amazon in Hollywood today, but still smokin'.
Ridley (Voice): Frank Welker - I mean come on. Frank Welker is just the go-to guy for voiceover work.
The Legend of Zelda
Link: The actor who played Peter in the two Narnia movies might work. The story would need to use the older Link (Zelda II, Twilight Princess) as kid Link would be stretching it. Biggest difficulty here is the common problem of adapting from this sort of source: would the wardrobe WORK in a movie? They may need to detail-up Link's garb, and the cap may be problematic....
Ganondorf: REALLY tough to cast, considering how tall he's supposed to be. Anthony Simcoe and Michael Dorn come to mind, but I don't know if you can get someone the right height without stunt-casting. It may take some CG or forced-perspective trickery to make it work. I'd envision the end battle as a blend of the hand-to-hand duel between Link and Ganondorf of Twilight Princess, and the final battle against his monstrous form, Ganon, in Ocarina of Time (for my money, the Ganon battle of OoT rates as THE most awesome boss battle of ALL time. There's just something that just makes it EPIC beyond anything I've ever played). Obviously, Ganon would need to be CGI rendered.
Half-Life
Dr. Gordon Freeman: Edward Norton
The G-Man: Johnny Depp - It was a toss-up between Depp and Downey. I have to say Depp, though.
Dr. Eli Vance: Morgan Freeman - Cameo or small role in Half-Life, expanded to more of a major player in the inevitable Half-Life 2.
Dr. Isaac Kliner: Ian Holm
Dr. Wallace Breen: Bernard Hill - Once again, a smaller role in Half-Life, before becoming the main villain in Half-Life 2.
Barney Calhoun - Ron Livingston