I can't believe it's taken this long for someone to address this issue.
I do feel a bit like my fourth wall is broken when shenanigans like this are pulled in a game, but I'm not sure I can really feel truly upset about it. I've never played HL2, E2, before, but this sounds like a relatively responsible use of legerdemain. Same for the MGS thing.
Looking back over my 19ish years of gaming, I find myself wondering where the implication that things must be interactive stems from. When I think back to the days of playing the licensed G.I. Joe video games on my NES, there certainly weren't any alternate endings or anything like that . . . there was just one ending, and when you sit down to play the game, the only question is whether or not you have the skill to unlock said ending.
I think perhaps this issue here is clarity. We, the players, do not like seeing backstage, which is what happens when the illusion is broken in situations like the above described. We want immersion in the video game experience, and when we see the tricks that bring us the cohesive experience, we feel a little cheated. It's one thing to be told how the magic happens in a making-of video, quite another to see wheels pop off while the wagon's rolling.
I also think that this is likely to happen because of concept I find personally execrable: hardcore gaming. I've met a fair number of people who compete against each other as much as the game itself. To achieve the ephemeral increase of self-worth that comes with besting their friends in competitive multiplayer modes, they have to practice and practice and practice, and if you stare at a work of art long enough, you'll eventually find the brushstrokes.
Personally, I think that isn't really a big deal. It is a ploy to wring emotion from us, true, but I WANT TO BE FOOLED. I am a player, I want emotions to come out of me when I play a game. If we're going to call the illusionists on this ploy, are we not honor-bound to call them on all others? What makes this trick worse than any other?