Music.
I dislike music that relies on vocals to do everything (eg most of the shitter mainstream stuff, each song is the same, its the different lyrics that define what the song is about). There are many instruments used in music, and voice is only one of them and to me its message is stronger and more obvious than the music beneath it. For that reason i think vocals should be used very wisely, to heighten or express small elements of the music... not to be the only message.
I personally dont think lyrics should be enough to know what a song is about. When i eventually get vocals on my album they will be very disconnected and very short lines. The music will remain the most important thing to tell the story. Each instrument will have its turn to be the focus of the story progression... instruments shouldnt automatically be backings for vocals.
So yeh, i notice the music first and foremost, and thats also the way most of the music i listen to (eg metal) is written to some degree (which is why i like it and listen to it i guess!) but vocals are very important and the small parts they should play in songs (by my rules) are often the most important parts, definitely the most memorable parts.