The gist of the argument: you might weep at a video game cut-scene, but the gameplay itself can never be all that emotionally involving. He has two articles on the subject: "A Game Has Never Made You Cry," and "No Tears for Mario."
From the first:
This is the nub of the issue here: a story can make you cry by empathising with the protagonist (or another character), but a game (when viewed as a formal system) cannot do this. It follows that the only way that a videogame can make you cry is by using narrative tools that have nothing to do with games as formal systems whatsoever. So even though, for instance, many people report that they cried when they played Final Fantasy VII at the fateful scene (and indeed, several other cRPGs also show up in player studies as having provoked tears) the moment that actually brought the player to tears was a non-interactive cut scene. It wasn't the game (in the systems view) that made them cry – it was the story – and there never was a question as to whether stories could make you cry. [more . . .]
I find this particularly interesting because I recently in this space attempted a defense, of sorts, of Simon Rafe, who featured in an exposé from the Catholic News Agency because he wrote fiction on the Internet, including a solo role-playing game. Subsequent to the CNA article, Rafe fell victim to the indignation of the Professionally Offended on the Internet Brigade, Catholic Division, because the CNA implied that his solo role-playing game contained prurient content (whether it did or not is unclear because it's no longer online and nobody, absolutely nobody, seems to have actually read or played the thing).
The argument I heard repeatedly from the Professionally Offended was that any "erotic content" is especially problematic in a role-playing game because such a game is more interactive than, say, a novel, and therefore it's okay to tear Rafe to pieces even though we don't actually know what he wrote. Although I'm not much of a gamer, I read Lone Wolf books back in the day and have some passing familiarity with solo role-playing games, so my answer is that they are less, not more, engrossing and involving than a regular book because the reader is repeatedly pulled out of the story in order to roll dice, do simple math, or maintain lists. Chris of Only a Game appears to be thinking along the same lines of what I had thought: interactive elements (what he calls the system) give the player something to do, but do not actually serve to make the story more engrossing. In fact, they may even distract the player from the story, the story being what actually carries the potential to get the player emotionally involved.
That, at least, gives one plausible reason why I'd rather watch someone else play a video game than play it myself. The other reason is that the other player, no matter who he is, is unlikely to die as often as I do.