The Prophet PBUH said:
نْ أَنَسِ بْنِ مَالِكٍ رَضِيَ الله عَنْهُ قَالَ: كَانَ لأَهْلِ الجَاهِلِيَّةِ يَوْمَانِ فِي كُلِّ سَنَةٍ يَلْعَبُونَ فِيهِمَا فَلَمَّا قَدِمَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ المَدِينَةَ قَالَ: "كَانَ لَكُمْ يَوْمَانِ تَلْعَبُونَ فِيهِمَا وَقَدْ أَبْدَلَكُمُ الله بِهِمَا خَيْرًا مِنْهُمَا: يَوْمُ الفِطْرِ وَيَوْمُ الأَضْحَى" أخرجه النسائي (1 / 231) ، والطحاوي في "مشكل الآثار" (2 / 211) ، وأحمد (3 / 103 , 178 , 235 , 250)
It was reported that the prophet PBUH said: In the days of Jahilia, there were 2 days a year that people used to celebrate and when the Prophet PBUH came into the Madina, he said you used to have 2 days to celebrate and Allah replaced them with 2 days that are better, Aldhua and Alfitr days.
There is also another hadith:
مَنْ تَشَبَّهَ بِقَوْمٍ فَهُوَ مِنْهُمْ ، وَمَنْ أَحَبَّ قَوْمًا حُشِرَ مَعَهُمْ " .
A person who does similar acts to certain people he is one of them, and whomever loves certain people he is risen with them in the day of Judgment.
Those two hadiths (and similar ones) are the ones some scholars use to say that it is not allowed to celebrate other holidays.
Personally, I think that if the celebrations are not religious in nature, it is fine. For example, the prophet celebrated the Day Allah saved Moses from the Jewish culture because we are more of his followers then they are.
Also keep in mind that the Majority of Muslims are Non-Arab and there are many converts and the only time they get to meet their family and friends (even Arab Muslims) except on National holidays.
Additionally, say celebrating "days" is OK but not holidays. For example many scholars said it was OK to celebrate national Labor day or independent day. From such ruling you can infer that any celebration that does not have to do with religion (ex: Christmas, Hanukkah or Halloween). There are many days people celebrate which have nothing to do with religion like Birthdays, thanksgiving, secretary day, etc... Which I personally think it is OK to participate in.