I agree about listening to just one genre of music, although I think I could probably categorize all the music I love into two or three broad categories based on the feeling I get listening to it. For personal interest, I will now attempt to do that:
The first category is epitomized by the first minute or two of
At the Drive In's Arcarsenal. It is intense, desperate and dramatic, the sound of the music becoming so energetic it seems to burst out of the musician's skin. Spasms of feeling. Included in it is stuff like The Mars Volta (De-Loused, Frances, Bedlam), Protest the Hero, These Arms Are Snakes, (earlier) Trophy Scars, Dizzy Gillespie's Afro, etc.
The next category is still intense, but it's a more subdued, graceful intensity. The emotion is there, but it is presented in a classier, more diginified way. Lyrical elegance and poignant melodies. Ice rather than fire.
Warning are the most obvious example of this. Others: Neurosis, Reverend Bizarre, La Dispute, Lana del Rey, Les Miserables, The Mars Volta's Noctourniquet, and Tool would be the first names that come to mind.
The last category is epitomized by
Sonny Rollins. It is music that sounds good and makes me happy. And I get the feeling that main purpose of the music is to sound good, rather than some sort of catharsis for ugly thoughts. There isn't a lot of drama or intensity to the songs, but it evokes good feelings and pleasant moods. Most of the jazz and stoner/doom-type stuff I listen to falls under this category: Taint, Zebulon Pike, Kenny Dorham, Sahg, Colour Haze, Causa Sui, Jex Thoth, etc.
After doing this I realize that there's lots of blurring between the categories but I can't think of anything that falls outside of them. Some bands even move between them... like I'd say that Opeth's first bunch of albums are category #2, while their last two are category #3.