To me, it seems almost impossible for anyone not to put emotion into their playing. I mean, just try it. Its pretty tough, so tough that I dont think any guiyarist would actually fall into a habit of doing it.
I think there are lots of stuff that make great guitarists, but my favorite qualities are technical skill, and by that I dont mean speed, tapping, etc, its how well you play what you play, and the feel of the song the artist creates. If a guitarist can make the guitar sound exactly the way he/she wants, then they are a good guitarist.