Albums.
If an artist is good, and the album is good, there's nothing like sitting back and listening to an entire album's worth of songs unwind. I know when I listen to an album for the first time, I can anticipate exactly what I want to hear next, and if it doesn't happen, I'm disappointed a bit. If the artist gets that and nails it, the album will flow better and the whole experience will be great.
Now, I'm going to sound like even more of a music snob.
Being a musician who formerly tried his hand at a serious music career (and failed miserably, I may add) track listing on an album is important. If you give a crap about the listener, you will want them to almost anticipate what is going to happen next. When we recorded our 5-song EP, we built it to flow and make the listener want to hang on until the last note of the last song. We had about 20 songs written at the time, and selected the strongest tracks for the EP, but carefully placed them to entice the listener to want to keep going. Even though I personally moved on stylistically from that genre of music (post hardcore), I can still listen to that EPand be happy with the results.
Great albums will start strong, let you settle in, smack you in the face to remind you that they are there, let you recover a bit again, and then close with a bang. Check out the show on VH1 Classic cleverly titled "Classic Albums". They do in-depth looks at the making of many classic albums, and they do a lot of hard rock and classic metal albums. So much stuff goes into making these complete masterpieces that you would never know. Some of the good episodes:
-Rush: 2112 and Moving Pictures (two for one!)
-Pink Floyd: Dark Side of the Moon
-Black Sabbath: Paranoid
-Motorhead: Ace of Spades
-Def Leppard: Hysteria
-Judas Priest: British Steel
-Phil Collins: Face Value
-Nirvana: Nevermind
-Deep Purple: Machine Head
There are a bunch more too.