Merry Christmas, Happy Chanukah, and whatever Kwanzaa's greeting is!
I don't like "Happy Holidays" as a saying. It's made to be as unoffensive as possible, and that's irritating. I'd rather someone say one of the above (whether to greet me as part of their holiday or mine) than say a catch-all term, which is why I've decided that I'm using "Generic Farewell!" as my response to "Happy Holidays."
The other thing that annoys me is that while we say such an unoffensive line, we also plaster Santa and other Christmas stuff all around it, completely destroying the point behind not saying "Merry Christmas" in the first place.
So until I see a commercial with a plain-clothed fat guy holding a dreidel and a kinara while wearing a santa hat and riding a magic mkeka while lighting a menorah and handing out toys and sweet potato pies to the kids, I won't consider "Happy Holidays" to be a thing.
Peace, Merry Christmas, and a Happy New Year!