User blog:SuperMario6/Unreleased Mario Games

Mario Bros. 2 (1984)
Supposed to be a sequel to Mario Bros. (1983). Several betas were released, but on December 1, 1984, glitches caused the NES beta to crash at Phase 10, postponing NES from April 17, 1985 to October 18, 1985, and cancelling Mario Bros. 2.

Super Mario Bros. 4 (1989)
With high sales of Super Mario Bros. 3, Nintendo of Europe was planning Super Mario Bros.