There are obviously all the top ones:
But the best social media website or platform is the one that is driving the best results for you. If you are a small crafts business that sells DIY tools, then Pinterest would be a great way to go!
If you are selling accounting services, Linkedin would be a great place to create content for and be on.
So figure out in your strategy what your gold and objectives are and what platforms will help get you closest to those!