If he wasn't held back, or moved back on purpose, he would have beaten Alonso a few times towards the end of last year. The raw results don't tell the story..
I think it's simply down to Massa taking 3/4's of a season to get on top of a car where Alonso can drive around a cars issues.
I imagine this year too by 3/4's distance Massa will start to be nearer Alonso, but who wants a driver who takes so long every year to get going? Massa will have his moments this year too, but the only sensible option is to run effectively one car if they want to get near a Red Bull.