I had some spare time so I tested what I had on my hard drive with the latest Dios mios.
It's not as organized as I'd like but it's readable. Maybe we can pool our resources and come up with a comprehensive list.
Working (no deal breakers):
Mario Sunshine - has had a slight issue with things all the way to the side vanishing.
Zelda OoT - yes really.
WarioWare - camera is a little weird but nothing game breaking or annoying.
Zelda Twilight Princess - some cutscenes look silly at the end/ Screen transitions only show 4:3 area
Kirby Air Ride - some menu oddities
Dragon Ball Z Budokai 2
Nicktoons Unite
Nicktoons Battle for Volcano Island
Mario Golf Toadstool Tour
Super Monkey Ball - Things disappear a little early off the side.
NBA Street V3 - players sometimes disappear when in plain sight on the side. In testing it wasn't so bad.
Beach Spikers
Sonic Heroes
Mario Kart Double Dash
Mario Party 7 - weird graphical issues nothing gamebreaking.
Shadow the Hedgehog
Paper Mario TTYD: transitions only happen in the 4:3 area, health bars for enemies and the "Y switch" icon are off center
Mega Man X Command Mission
Mario Party 6 - minor menu oddities
Mario Party 5 - Character bubbles are really screwed up. Otherwise fine.
Animal Crossing
Big issues:
Wario World - things dissappear off the side a little bit too much.
????
Mario Baseball - possible stretching. Having trouble telling.
Won't boot:
Mario Party 4
Viewtiful Joe 2
Viewtiful Joe
Mario Power Tennis
Has native support:
https://en.m.wikipedia.org/wiki/List_of_GameCube_games_with_480p_and_16:9_support
Games with cheat codes:
Super Smash Bros. Melee
Needed: games with 16:9 cheat codes
It's not as organized as I'd like but it's readable. Maybe we can pool our resources and come up with a comprehensive list.
Working (no deal breakers):
Mario Sunshine - has had a slight issue with things all the way to the side vanishing.
Zelda OoT - yes really.
WarioWare - camera is a little weird but nothing game breaking or annoying.
Zelda Twilight Princess - some cutscenes look silly at the end/ Screen transitions only show 4:3 area
Kirby Air Ride - some menu oddities
Dragon Ball Z Budokai 2
Nicktoons Unite
Nicktoons Battle for Volcano Island
Mario Golf Toadstool Tour
Super Monkey Ball - Things disappear a little early off the side.
NBA Street V3 - players sometimes disappear when in plain sight on the side. In testing it wasn't so bad.
Beach Spikers
Sonic Heroes
Mario Kart Double Dash
Mario Party 7 - weird graphical issues nothing gamebreaking.
Shadow the Hedgehog
Paper Mario TTYD: transitions only happen in the 4:3 area, health bars for enemies and the "Y switch" icon are off center
Mega Man X Command Mission
Mario Party 6 - minor menu oddities
Mario Party 5 - Character bubbles are really screwed up. Otherwise fine.
Animal Crossing
Big issues:
Wario World - things dissappear off the side a little bit too much.
????
Mario Baseball - possible stretching. Having trouble telling.
Won't boot:
Mario Party 4
Viewtiful Joe 2
Viewtiful Joe
Mario Power Tennis
Has native support:
https://en.m.wikipedia.org/wiki/List_of_GameCube_games_with_480p_and_16:9_support
Games with cheat codes:
Super Smash Bros. Melee
Needed: games with 16:9 cheat codes