This is a list of games with widescreen (16:9) video output support in the 5th generation of game consoles or earlier.  Only pre-6th generation games will be listed to present console games released before widescreen TVs and monitors were common.

The vast majority of these games use the anamorphic 16:9 format as their widescreen modes.  So you'll need to set your TV/monitor to stretch the image to full screen to get your game to display correctly. Some games, though, were letterboxed in widescreen; so in such cases you'll need to set your TV/monitor to crop or zoom the image in order to get full widescreen video output.

Special thanks to Genesis Knight  for contributing to the Saturn, Genesis and Sega CD lists.
Special thanks to A Black Falcon, EddieJ1984 and cheaterdragon1 for contributing to the N64 list.

Sega Mega Drive/Sega Genesis (1988 Hardware)
World Cup USA 94 (1994) (anamorphic 16:9 option) 

Total: 1 game

Mega CD/Sega CD (1991 Hardware)
The Ninja Warriors (1993) (forced letterbox 4:3; requires crop/zoom TV function for fullscreen)
World Cup USA 94 (1993) (anamorphic 16:9 option)

Total: 2 games

Super 32X/Mega 32X/Sega 32X (1994 Hardware)
Virtua Fighter (1995) (anamorphic 16:9 option)

Total: 1 game

Sega Saturn (1994 Hardware)
All-Japan Pro Wrestling featuring Virtua (1997) (anamorphic 16:9 option)
Baroque (1998) (anamorphic 16:9 option)
Christmas NiGHTS (1996) (anamorphic 16:9 option)
NiGHTS Into Dreams... (1996) (anamorphic 16:9 option)
Panzer Dragoon II Zwei (1996) (anamorphic 16:9 option)
Stellar Assault SS (1998) (forced letterbox 4:3; requires crop/zoom TV function for fullscreen)
Touge: King the Spirits (1995) (anamorphic 16:9 option)
Touge: King the Spirits 2 (1997) (anamorphic 16:9 option)

Total: 8 games

Sony Playstation (1994 Hardware)
Aqua GT (anamorphic 16:9 option)
Bloody Roar 2: Bringer of the New Age (anamorphic 16:9 option)
C3 Racing/Max Power Racing (letterbox 4:3 option/anamorphic 16:9 option)
Codename Tenka (anamorphic 16:9 option)
Colin McRae Rally (anamorphic 16:9 option)
F1 2000 (anamorphic 16:9 option)
F1 Championship Season 2000 (anamorphic 16:9 option)
Formula 1 (anamorphic 16:9 option)
Formula 1 98 (anamorphic 16:9 option)
Ghost In The Shell (anamorphic 16:9 option)
J's Racin' (1997) (anamorphic 16:9 option)
J-League Jikkyou Winning Eleven 2000 (anamorphic 16:9 option)
J-League Jikkyou Winning Eleven 2000 2nd (anamorphic 16:9 option)
J-League Jikkyou Winning Eleven 2001 (anamorphic 16:9 option)
J-League Jikkyou Winning Eleven 3 (anamorphic 16:9 option)
J-League Jikkyou Winning Eleven '98-'99 (anamorphic 16:9 option)
JGTC: All-Japan Grand Touring Car Championship (1998) (anamorphic 16:9 option)
Moto Racer World Tour (anamorphic 16:9 option)
Ms. Pac Man Maze Madness (anamorphic 16:9 option)
Need for Speed: Porsche 2000 (anamorphic 16:9 option)
Pac-Man World (anamorphic 16:9 option)
Puzzle Bobble 3 DX (anamorphic 16:9 option)
Racingroovy VS (anamorphic 16:9 option)
Rush Hour (anamorphic 16:9 option)
Snow Racer '98 (anamorphic 16:9 option) (through code, see www.gamefaqs.com/ps/930722-snow-racer-98/cheats)
This is Football (anamorphic 16:9 option)
This is Football 2 (anamorphic 16:9 option)
TNN Motor Sports Hardcore TR (letterbox 4:3 option/anamorphic 16:9 option)
TOCA Championship Racing (anamorphic 16:9 option)
TOCA World Touring Cars (anamorphic 16:9 option)
Touge Max: Saisoku Driver Master (anamorphic 16:9 option)
Triple Play 2000 (anamorphic 16:9 option)
Triple Play 2001 (anamorphic 16:9 option)
Triple Play Baseball (anamorphic 16:9 option)
V-Rally Championship Edition 2 (anamorphic 16:9 option)
Wip3out (anamorphic 16:9 option)
Wip3out: Special Edition (anamorphic 16:9 option)
World Soccer Jikkyou Winning Eleven 3: World Cup France '98 (anamorphic 16:9 option)
World Soccer Jikkyou Winning Eleven 4 (anamorphic 16:9 option)
Worms Armageddon (anamorphic 16:9 option)
Yarudora Series Vol. 1: Double Cast (letterbox 4:3 option/16:9 friendly option)
Yarudora Series Vol. 2: Kisetsu o Dakishimete (letterbox 4:3 option/16:9 friendly option)
Yarudora Series Vol. 3: Sampaguita (letterbox 4:3 option/16:9 friendly option)
Yarudora Series Vol. 4: Yukiwari no Hana (letterbox 4:3 option/16:9 friendly option)

Total: 44 games

Nintendo 64 (1996 Hardware)
007: The World is Not Enough (anamorphic 16:9 option)
Armorines: Project S.W.A.R.M. (letterbox 4:3 option; requires the expansion pack; requires crop/zoom TV function for fullscreen)
Army Men: Sarge's Heroes (letterbox 4:3 option; requires crop/zoom TV function for fullscreen)
Army Men: Sarge's Heroes 2 (letterbox 4:3 option; requires crop/zoom TV function for fullscreen)
Banjo-Tooie (anamorphic 16:9 option)
Daikatana (letterbox 4:3 option; requires the expansion pack; requires crop/zoom TV function for fullscreen)
Donkey Kong 64 (anamorphic 16:9 option; requires the expansion pack)
Excitebike 64 (letterbox 4:3 option; requires the expansion pack; requires crop/zoom TV function for fullscreen)
GoldenEye 007 (letterbox 4:3 option/anamorphic 16:9 option; "Full", "Wide" and "Cinema" options for each aspect ratio)
Hybrid Heaven (anamorphic 16:9 option)
Jet Force Gemini (letterbox 4:3 option; requires crop/zoom TV function for fullscreen)
Ken Griffey Jr's Slugfest for N64 (letterbox 4:3 option; requires crop/zoom TV function for fullscreen)
Mickey's Speedway USA (letterbox 4:3 option; requires crop/zoom TV function for fullscreen)
Perfect Dark (letterbox 4:3 option/anamorphic 16:9 option; "Full", "Wide" and "Cinema" options for each aspect ratio)
Road Rash 64 (letterbox 4:3 option/anamorphic 16:9 option)
South Park (letterbox 4:3 option; requires the expansion pack; requires crop/zoom TV function for fullscreen)
Starshot: Space Circus Fever (letterbox 4:3 option; requires crop/zoom TV function for fullscreen)
Stunt Racer 64 (letterbox 4:3 option; requires crop/zoom TV function for fullscreen) 
Superman: The New Superman Adventures (letterbox 4:3 option; requires crop/zoom TV function for fullscreen)
Top Gear Overdrive (letterbox 4:3 option; requires crop/zoom TV function for fullscreen)
Turok: Rage Wars (letterbox 4:3 option; requires the expansion pack; requires crop/zoom TV function for fullscreen)
Turok 2: Seeds of Evil (letterbox 4:3 option; requires the expansion pack; requires crop/zoom TV function for fullscreen)
Turok 3: Shadow of Oblivion (letterbox 4:3 option; requires the expansion pack; requires crop/zoom TV function for fullscreen)
World Driver Championship (letterbox 4:3 option; requires crop/zoom TV function for fullscreen) 

Total: 24 games