I listen to a lot of music (mostly progressive stuff), but I really only care about three bands:
1. Symphony X
Favorite band, hands down. To say I am obsessed with their music would be an understatement. Their self-titled debut was a bit of a stinker (99% of this was the vocalist), but everything else is pure gold.
2. Opeth
Loved them since 2004. Their sound is so haunting and beautiful. All their albums are great, but I recommend Still Life, Damnation, and Morningrise. I thought My Arms Your Hearse was overrated.
3. Seventh Wonder
Got into them a few years back when I heard Waiting in the Wings (I still prefer it to Mercy Falls). The Great Escape might top it, though! I can't get enough of this album!
Some other bands I listen to, although not nearly as much as the three above:
* Adagio - Neoclassical progressive metal from France. Four albums, all quality.
* Anthriel - New Finnish prog metal band. Debut album The Pathway is quite good; Symphony X-type sound.
* Armored Saint - One of the few 80's metal bands I still listen to. I recommend Symbol of Salvation (massively underrated; probably one of the greatest metal albums of all time).
* Avantasia - Multi-vocalist side project from the Edguy frontman. Good symphonic metal.
* Black Sabbath - Dio stuff only; can't stand Ozzy's voice.
* Circus Maximus - Great prog metal band from Norway; both albums are good.
* Bruce Dickinson - Iron Maiden vocalist side project. Chemical Wedding is a fantastic album; one of my favorite metal albums for sure!
* Dio - Has some great stuff from the 80's; Holy Diver, Last in Line, etc. Perfect for karaoke!
* Dream Theater - Occasionally; can only take them in small doses. First four albums are fantastic, but then they go downhill (although Train of Thought is a diamond in the rough). Rudess is a bit too experimental for me at times with all his weird-sounding space patches; give me classical sounds any day over that. Also, after listening to great singers like Russell Allen and Tommy, LaBrie annoys the never-ending shit out of me...
* Iced Earth - When I'm in the mood for cheesy power metal. Horror Show (their last good album) is one of my favorites.
* Iron Maiden - I actually prefer their latest albums (2000 onward) to their classic stuff; I find it to be more consistent. Brave New World is easily one of my favorite albums of all time.
* Kiuas - Finnish metal band with a wide range of influences. Check out Reformation.
* Kamelot - Once again, when I'm in the mood for cheesy power metal. Sometimes a bit over-dramatic for me.
* Liquid Tension Experiment - Dream Theater without the vocals! Win-win! No Myung though.
* Nightwish - I actually prefer their new singer to Tarja, but their back catalog is decent.
* Pink Floyd - My favorite is Animals, and I think Dark Side of the Moon is overrated.
* Rainbow - More Dio! Their albums from '75 to '78 were excellent!
* Rush - Classic prog rock. They have like 20 albums; there's got to be something in there that everyone can like (unless you can't stand Geddy's voice). I like their 80's period.
* Joe Satriani - Probably my favorite instrumental rock music. Check out Crystal Planet or Strange Beautiful Music.
* Threshold - British prog rock/metal band with several great albums; I recommend Hypothetical and Subsurface.
* Time Requiem - Swedish power metal with neoclassical influences. About 50% good.
Those are just some of the artists I like. I also enjoy a lot of video game music, particularly from the Resident Evil and Metroid series.