Now, my main objection to the 'celebration of greed' criticism is that it only really applies to the people who raise it. Not everybody goes into Christmas thinking "Oh, I can't wait to get all the toys!" children might, but they're children so that's okay, but to anyone older than fifteen Christmas will be a lot more than that. If you think people enjoy Christmas only for the fact that people give them loads of stuff, then that's probably because you can't see any value in the holiday beside the gifts. The best thing, for me (and I'm sure many others) is the buying of gifts for all of your family and friends. Either buying what they've told you they would like, or using your imagination to think up an awesome gift for people is a truly wonderful part of the holiday season.
What Christmas is, is a celebration of nostalgia and love for others. Everyone has their own little routine for Christmas, one which they've likely had for years, we look forward to it because it reminds us of Christmases from the past, which we really enjoyed and will continue to enjoy as we celebrate it every year... Christmas is not a celebration of greed, and anybody who claims that it is is must be awfully pessimistic.