I think its both.

Yes the origins in most of the holidays are Pagan, but they are now reworked and recognised by Christians and they symbolise and celebrate their faith. Even the celts have parts of their faith that was passed down from other areas such as Nordic Pagan faiths. Its not the first time in history its happened so I don't think there's need for crucifying (no pun intended) Christians due to some similarities. I think its important to appreciate the history of your faith, but not necessary to be compared in some elitist way.

Whilst I'm not Christian myself, I love Father Bob's take on all this he has some great (and funny) interpretations.

Christianity is a modern religion when you really think about it. Given Judaism and Islam were the faiths of god prior to the life of Jesus.