There's no 'metric' for 'how invested I get in games'; It depends entirely upon the game and how it is presented by the GM. I've been in a 4E game that was basically a guy reading from a module, and let me tell you, I was not invested. I've also been in games in a bunch of other systems in which I was -very- invested.

That said, in my experience, most players are not metagaming jackasses. DM of the Rings is hyperbole. Of course, this board is a useless sample, because metagaming jackasses seldom seek out internet forums to discuss gaming.

Have you tried actually talking to your players like intelligent human beings and asking them why they're not invested in the game?