Super Mario Wiki page on Paper Mario's pre-release and unused content, mentions Super Mario RPG 2.

Super Paper Mario (lost build of unreleased original GameCube version of Wii side-scrolling platformer 2006).

Super Mario World (partially found early build of Super Nintendo platformer 1989).

Super Mario World: Mario Attack (lost Japanese arcade game 1996).

Super Mario's Wacky Worlds (found prototype of cancelled CD-i game 1993).

Originally, the game was conceived using generic characters, including a man wearing overalls. However, due to the limitations of the Super NES, having such elaborate tracks in a multiplayer game would not have been possible.

Super Mario Spikers (lost build of cancelled Wii volleyball-wrestling sports game 2007) Super Mario Kart was originally conceived as a two-player version of F-Zero.

Super Mario Kart R (partially found pre-release version of 'Mario Kart 64' 1995).

Super Mario Disk Version aka 'Super Mario 64DD' (found unreleased Nintendo 64DD port of 3D platformer 1999).

(lost Commodore 64 port of NES platformer existence unconfirmed 1986) 3 (lost Japanese prototype of NES platformer 1987-1988)

Super Mario 64 (partially found Spaceworld '95 demo of Nintendo 64 3D platformer 1995).

Super Mario 128 (lost build of cancelled GameCube/Wii game 2000-2006).

(lost early builds of Nintendo DS 2D platformer 2004-2006)

Mario Takes America (lost build of cancelled Philips CD-i edutainment game 1992-1994).

Mario Kart XXL (lost Game Boy Advance tech demo 2004).

Mario Motors (lost build of unreleased Nintendo DS racer early 2000s).Mario's Face (lost Nintendo DS tech demo 2004).Mario Demo (lost Virtual Boy tech demo 1994).

Mario's Castle (lost build of cancelled game on Nintendo's 'Project Atlantis' handheld console existence unconfirmed 1995-1998).

Mario Artist (lost builds of unreleased Nintendo 64DD games 1999-2000).

BS Super Mario Collection (partially lost Satellaview broadcast versions of compilation platformer 1997-1998).

Nintendo 64 Disk Drive (partially found unreleased video games for Nintendo 64 add-on late 1990s-early 2000s).

A screenshot of Nintendo Power issue 104, where a reader asks a question about sequels to Super Mario RPG, Super Mario 64, and Donkey Kong Country for the Nintendo 64.

Super mario kart 64 game art