I've worked at large companies that do both B2B and B2C.
B2C gets 90% Google logins, 10% email logins, and small amounts of Twitter, Facebook, Microsoft, etc logins.
B2B is different. I forget the numbers but you get more email logins, Microsoft logins, and company SSO logins. Google and email were the still the top from what I saw.
If I were building a site today, I'd start with Google and email, with a plan to expand to more providers including SSO for the big enterprise customers if I was doing B2B.