I don't like Christmas, because once you stop believing in Santa, everyone stops trying to be good and gets presents anyway. I was Buddy the Elf for Children's Theater at my school, and it makes me wish that everybody just cared about each other, regardless of whether the person thinks they're an elf or not, etc. As for commercializing Christmas, yes, it is commercialized. I think "holiday spirit" incorporates the birth of Jesus(whether or not it's his real birthday! ::) ), the spirit of giving, and being cheeful towards everyone. People SHOULD be cheerful to everyone, the way suicide rates increase during the holiday season.
My favorite part of Christmas, besides the birth of Jesus: Manheim Steamroller's Deck the Halls.