I do think there's new ground to break in shooters. For instance, consequences. In a HL2 demo video, you could knock something over during a "cutscene"-esque part and Kleiner would stop what he was doing and say "careful with that Gordon". Half Life has a rich cast of characters, and in the first game you could control some of their movements, hear a bit from them, and guard them. In HL2, I thought that would be expanded, with a better set of ways of communicating with the other characters, making decisions that affected them, that sort of thing. Instead, when one character does predictable betrayal, you can't even stop them from escaping even though their in perfect gun range.
If games want to be more real, one gulf they have yet to even start crossing is more realistic interaction with the people in the games, ways to talk, influence, learn from and cooperate with. If Valve want us to to feel HL3 is more "real", they could start by making it so it actually feels we're part of a team with a common purpose, not just a guy standing around a stage while everyone recites their lines.