It's true. Nothing celebrates more than Diwali. It's a Hindu place. In the south resides some Christians, so it's a good get together. Otherwise, it doesn't make friction towards celebrating Thanksgiving and Christmas.
Regarding your question Vellichor, family. We celebrate big every year. All siblings at my mom's house with some extended family. Only way I know how to celebrate it.
There are almost 30 million Christians in India, making it the country's third largest religion. Obviously they also celebrate Christmas. There's even Indian Christian folklore.