I'm a foaming at the mouth Dream Theater fan. I drove over a hundred miles to talk to Mike Portnoy for 5 minutes and shake his hand in a meet-and-greet. DT and all the related side projects/friends/touring partners make up 25% of my listening.
Aside from that I mainly like rock/metal from the 1980's/1990's - Iron Maiden, Rush, Sabbath, Metallica, etc. I'm such a music excentric it's easier to narrow down what I don't like, and assume I like the rest. I've learned that the old computer proverb: "Garbage in, Garbage out" holds true with music and life in general. I don't listen to anything that's based in negativity, darkness or hatred, no matter how good the musicians are. I used to love King Diamond, until I realized what he was saying.
Mostly everything except the following:
Satanic poser metal. (Or real satanic/death metal, but I think 99% of them are just posers that watched one too many horror films)
Gangsta rap/hiphop that denegrates and is based in selfishness and ego (look at me and how much bling/ho's I have). I like rap and hiphop that's fun and positive - Will Smith, Alicia Keys. Eminem is extremely talented, but his overall message is negative.
Italian Opera - Fingernails on a chalkboard. German opera is great - more dynamics, less overdone vibrato. Italian opera is the vocal equlivalent of me swinging my tremolo furiously on every note.
"Smooth" Jazz - Irritating easy listening with a monotonous up-tempo computer drum beat and some putz wailing on a soprano sax. - yuk. I like real jazz - Miles, Coltrane, Brubeck, Marsalis, Stanley Clarke, etc. I especially Nat King Cole's intrumental piano work from the 1940's.
I don't really care for a lot on modern alternative rock - too whiny and simplistic for me - all energy, no songwriting skill.
Overall, I love most music - from Madonna to Mozart to Motley Crue.