Being a Pagan, I find it interesting how many holidays are derived from ones started by Pagans in ancient times. It really is fascinating. Samhain along, an October holiday/ritual that honors the dead became both Halloween and Mexico's Day of the Dead, though the later is closer in spirit to what we do. Christians turned Yule into Christmas, and at the core it's pretty close in many ways, basically spending the darkest days of the year with loved ones, having a little feast, and maybe exchanging a gift or two.
I honestly think that unless humans are being sacrificed, holidays are a good thing. They are basically pressure relief valves and allow us to unwind and have a little fun. Even if religion someday goes away altogether, keeping a few holidays around isn't a bad idea.