Half-life didn't really have a plot in the traditional sense. I mean, it's not a story that's shoved in your face. All the characters talking to you is just setting the scene. What do people do when the scientists are jabbering on? Run around jumping on things, trying to climb on pipes/crates etc. At least, that's what I did. The great games focus on the game mechanics and lead the character through a series of events. The plot is secondary really.
Another example: Dishonoured - great game. Can't remember the story one bit but I do remember the characters, the scenary, the neo gothic architecture. In essence, the visual stuff.