First-off, anyone with a PC who hasn't yet played Half-Life is a fool. Go buy it and play it. Now. The game is a mix of first-person shooter and puzzle solver, with varying scenery and a shedload of characters and alien creatures. Yeah, it's a bit old now, and the graphics do look old, but the game is good enough that you won't care about that after an hour. Just go play it, and possibly the expansion packs Opposing Force and Blue Shift. Then come back and read the following (which contains plot spoilers for anyone who hasn't yet played the game) and agree that Half-Life could, if handled right, make a great movie.
Okay, here's the pitch.
Gordon Freeman rides the monorail to work at the Black Mesa research complex, dons his hazardous environment suit and heads into the test chamber. An aggressive test on a piece of “anomalous material” triggers a resonance cascade, a violent reaction that causes several portions of spacetime to mingle.
Gordon awakes in the ruined test chamber, fire and smoke and sirens, and sees scientists badly injured. Heading off to look for help, he realises that the resonance cascade has had effects that reach well beyond the test chamber.
Presumably because of the HEv suit's airtight nature, Gordon Freeman never speaks. Think of him as the strong, crowbar-wielding, silent type. His adventures are based around being directed by one terrified scientist after another, in the hope of closing off the rift in spacetime. He fends off alien creatures, US Marine squads sent to cleanse the facility, and government special-ops soldiers who have their own orders and who view everyone as expendable.
At the same time, the script should follow the story of Corporal Adrian Shephard [from the Opposing Force expansion pack]. His team of Marines have been shot down, crash landing into the midst of the carnage at Black Mesa. They never received their orders, so they do their best to fight off alien hordes while trying to find military command. When the tide of battle turns against the human forces, Corporal Shephard's team try to escape the facility, only to be abandoned to their fate by their superiors. As the Corporal's team is reduced in numbers, Shephard realises that human special-ops soldiers are just as much a threat to him as the alien forces are.
Alongside Freeman and Shephard, the script ought to feature the adventures of Barney Calhoun [from the Blue Shift expansion pack], a security guard who arrives at work, only to plummet down an elevator shaft when the resonance cascade causes violent tremors to shake Black Mesa. But Barney is a hardy fellow, so he dusts himself off and readies his pistol. Running into a group of scientists hiding from the violence, he helps them escape to an abandoned facility. In order for the scientists to reactivate a prototype teleporter, Barney has to roam around getting things ready in the hope that they can all teleport out of Black Mesa. And he does it all with a smile.
All three parts of the Half-Life gaming experience feature sections where the characters teleport to the alien world Xen. I think having all three characters visit Xen would be overkill for the movie, but others might disagree. What wouldn't be in dispute, though, is how to end the movie. Gordon Freeman's task is vital: he needs to destroy the Nihilanth that is holding open the spacetime rift, in the hope of sealing off the invasion. And his final meeting with the mysterious G-Man is a great way to end the movie.
The Half-Life games really are rich with characters, creatures, action, violence, compassion and story. I'm sure that Half-Life could make an incredible movie, but only if it was written and created by people who had played the games and taken a lot of notes. If I had connections in the movie business, I'd be pushing for it to happen. Hopefully someone actually in the movie business is already eyeing this one up.
The following would be unwelcome in a movie version of Half-Life:
2010-10-21: Looks like I'm flogging a dead horse here, for two reasons. Firstly, plenty of Hollywood types have already tried to pitch a Half-Life movie, and done a bad job of it. And secondly, Valve are thinking that maybe they should make the movie themselves. This is according to an interview in PC Gamer.