Sometimes silent protagonists work. I can understand why it would be used in something like a FPS, but I think they've certainly reached a point where you could have a character speak while in first person and know without a doubt that it's your character speaking. That would enable more development and strong characterisation, which always helps with the crafting of deeper stories.
One of the benefits of RPGs, though, is being able to choose the type of character you play, so having selectable dialogue is good then. In Fallout 3, for example, having them be silent worked because I was able to imagine their voice and the way in which it was delivered; it was my character and I didn't really want anyone else interfering with my perception of them. That character was an extension of myself and what I felt like doing.
But, in a game like Mass Effect, having Shepard be fully voiced with dialogue choices was a brilliant decision; it worked because you were playing a character that was completely fleshed out and fit perfectly within the story, but you had enough say in what they were doing to resemble your own thought processes and to experience Shepard in ways that made him/her more sympathetic or interesting to you. It's still always Shepard, and they're still always the hero, but it reflects different methods of achieving your ends in the greater scheme of things.