According to the World Association of Newspapers [1], they are Yomiuri Shimbun, Asahi Shimbun, and Mainichi Shimbun; also, those are the largest newspapers in the world. In terms of political leanings, Yomiuri is conservative, Asahi is liberal, and Mainichi is somewhere in-between.

[1] http://www.wan-press.org/article2825.html