Yes, supermarkets is like trench warfare in WW1 - one month one side captures a trench, while the next month it is captured back.
As a group, the three FTSE100 supermarkets look attractive. Individually they also look attractive.
In 2010, utilities dominated my portfolio. During 2011 it was pharmaceuticals. Now it's food retail.
By holding all three, I don't have to care which do well or badly, but, I suspect that all three supermarkets will at least match and probably outperform the FTSE on a five-year view.