This is a great subject to think about, although it's really hard one.
The single greatest moment and a song last year was absolutely Pixies and 'Where is My Mind'. I had waited for that moment since I heard Pixies for the first time many years ago. I even had to shed a few tears during the song...It was so beautiful!!
Now, I would really like to experience something like that also this year. Sufjan Stevens is the one I mostly await. 'Chicago' is the song I would love to hear live and also 'I Walked' is important for me.
Other important artists and songs are at least
Galaxie 500 - Strange
Ariel Pink - Round and Round
John Cale - Macbeth
M. Ward - Poison Cup
Gang Gang - House Jam
Fleet Foxes - Your Protector
Animal Collective - For Reverend Green
Pere Ubu - 30 Seconds Over Tokyo
Pulp - Dishes
Well, there for starters.