That depends on who can buy ownership stake, and who is the purpose of the company serving. If it explicitly exists to benefit it's investors, then the effective owner might also be the public. But you're right, if we are talking about legal ownership, it might relate to who has an ownership stake.

Although, it's possible for the largest public investor to become the owner as well.

I guess my fundamental point is that they aren't the private property of a single person. Corporations are not sole proprietorships.