Id touted its hiring of professional SF writer Matthew Costello to flesh out the story of Doom 3; but in the end it's just a lot of details grafted onto the basic (non)plot of the original Doom. Half-Life 2 not only features good SF, but good storytelling all around. It's modelled after a movie, with memorable scenes and dramatic set pieces as part of the game, not just cutscenes that you sit back and watch. It begins with a 1984-like opening: depressed people wearing coveralls as they move about a dilapidated city, Big Brother (Dr Breen) prattling on from the giant viewscreen that hangs in the city square. It culminates in the infiltration of The Citadel, a structure whose sheer size elicits that "sense of wonder" that SF has the potential to do so well.

When the original Doom came out, the highlight of the game was the first appearance of the Cyberdemon. He was huge, deadly, and accompanied by the unnerving piston sound of his legs. (For some strange reason, he was the second-to-last boss. id elected to feature the Spider Mastermind as the grand finale.) But the Cyberdemon's re-appearance in Doom 3 is anti-climatic. He seems even larger, and he's certainly more detailed. But the surprise is gone, and in the end he's just a big monster lumbering after you.

Despite being blatantly inspired by the Martian war machines of The War of the Worlds (actually, because of it), Half-Life 2 introduces one of the greatest aliens in gaming history: the striders. Towering tripodal creatures, they're not only armed with deadly firepower, but have the ability to duck and weave. It's the perfect melding of design and movement.

As far as the narrative structure goes, Doom 3 made the questionable decision to send the main character to Hell...and then return him to Mars to continue running through corridors. It felt like a step backwards. The only place where Half-Life 2 fails structurally is the ending. Valve deserves credit for avoiding the predictable and increasingly tiresome tradition of an endgame boss; instead, they opt for a climax that makes sense from a narrative standpoint. But their alternative is unimaginative and unexciting. This is compounded by the reappearance of the mysterious G-Man who spouts something cryptic before exiting the scene. Considering it was six years since the first Half-Life, this is a major disappointment, as it does little to answer any questions or push the overall story further. Here's hoping that Valve offers up some sort of resolution with Half-Life 3.