I used to be on a photo-page where I a guy from Iceland took the sweetest landscapes, and the only setup he used was 1ds II and a 12-24 Sigma. So I guess the wider the better!
I would bring (on a 60d) a 10-22 Canon and a 70-200 f4 L.
I'm going to Iceland myself, hopefully next summer, as I know some people who have relatives there. And my choice of setup then will my trusted TS-E 17mm and a brand new 1d X