Here's a cool summary of the systems covered by RetroPie, in chronological order!

Arcade Systems, Game Consoles, and Home Computers in RetroPie

YEAR OF RELEASE	PICTURE	NAME	TYPE	EMULATOR
1977		Atari 2600	Game Console	Stella(RetroArch)
1977		Apple II	Home Computer	LinApple
1977		Commodore PET	Home Computer	Vice
1979		Atari 800	Home Computer	Atari800
1979		Intellivision	Game Console	jzintv
1979		Z-machine	Virtual Machine	Frotz
1980		Commodore VIC-20	Home Computer	Vice
1981		IBM PC	Home Computer	rpix86
1982		Commodore C 64	Home Computer	Vice
1982		Commodore CBM-II	Home Computer	Vice
1982		Vectrex	Game Console	Vecx(RetroArch)
1982		ZX Spectrum	Home Computer	Fuse FBZX
1983		MSX	Home Computer	OpenMSX
1983		Nintendo Entertainment System	Game Console	FCEUMM(RetroArch)
1984		Apple Macintosh	Home Computer	Basiliks II
1984		Amstrad CPC	Home Computer	CPC4Rpi
1984		Commodore Plus/4	Home Computer	Vice
1985		Commodoce 128	Home Computer	Vice
1985		Commodore Amiga	Home Computer	UAE4ALL
1985		Atari ST	Home Computer	Hatari
1985		Sega Master System	Game Console	Picodrive(RetroArch)
1985		Sega System 16	Arcade	Final Burn Alpha
1987		TurboGrafx-16	Game Console	Mednafen(RetroArch)
1988		Sega Genesis	Game Console	Picodrive(RetroArch)
1988		CP System	Arcade	Final Burn Alpha
1989		Atari Lynx	Handheld	Handy(RetroArch)
1989		Game Boy	Handheld	Gambatte(RetroArch)
1990		Sega Game Gear	Handheld	Osmose
1990		Neo Geo	Arcade	Final Burn Alpha
1990		Super Nintendo Entertainment System	Game Console	PocketSNES(RetroArch)SNES9X PiSNES
1991		Sega CD	Game Console	[Picodrive(RetroArch)
1993		CP System II	Arcade	Final Burn Alpha
1994		Sega 32X	Game Console	Picodrive(RetroArch)
1994		Sony Playstation	Game Console	PCSX Rearmed(RetroArch)
1996		CP System III	Arcade	Final Burn Alpha
1996		Nintendo 64	Game Console	Mupen64plusMupen64plus-libretro
1998		Game Boy Color	Handheld	Gambatte(RetroArch)
2001		Game Boy Advance	Handheld	GPSP
2001		ScummVM	Virtual Machine	ScummVM
2004		C64 Direct-to-TV	Game Console	Vice