Genesis USA games that use 256x224 mode during main gameplay. List created & tested by Firebrandx (wolff@firebrandx.com) Updated March 27, 2019. 


3 Ninjas Kick Back ...................................(Sega and Psygnosis logos in 320 mode)
Addams Family, The
Adventures of Mighty max, The
Adventures of Rocky and Bullwinkle, The
Aerobiz
Aerobiz Supersonic ...................................(Sega logo in 320 mode)
Air Buster
Arrow Flash ..........................................(Sega logo in 320 mode)
Ayrton Senna's Super Monaco GP II.....................(all except stage select and race in 320 mode)
B.O.B. ...............................................(EA logo in 320 mode)
Barbie Super Model
Barkley Shut Up and Jam 2 ............................(player select & versus screen in 320 mode)
Barkley Shut Up and Jam!
Bass Masters Classic - Pro Edition
Batman Forever .......................................(Probe logo in 320 mode)
Beast Wrestler .......................................(Sega logo in 320 mode)
Beavis and Butt-Head
Best of the Best .....................................(logos in 320 mode)
Bible Adventures
Bonanza Brothers .....................................(Sega logo in 320 mode)
Bubble And Squeak
Bubsy in - Claws Encounters of the Furred Kind
Bugs Bunny in Double Trouble 
Caesars Palace
Captain America and the Avengers .....................(Sega logo in 320 mode)
Captain Planet and the Planeteers
Championship Pool
Championship Pro-Am ..................................(Sega logo in 320 mode)
Chase H.Q. II ........................................(Sega logo in 320 mode)
Chavez II
Chester Cheetah - Too Cool to Fool ...................(Sega logo in 320 mode)
Chester Cheetah - Wild Wild Quest ....................(Sega logo in 320 mode)
Chi Chi's Pro Challenge Golf .........................(Sega logo, intro, & title screen in 320 mode)
Clay Fighter
Cliffhanger
Clue .................................................(Sega logo in 320 mode)
Cross Fire
Cutthroat Island .....................................(Sega logo & copyright in 320 mode)
David Crane's Amazing Tennis
Deadly Moves
Devilish - The next Posession
Dino Land ............................................(Sega logo & title screen in 320 mode)
DJ Boy
Double Dragon 3 - The Arcade Game ....................(all except main gameplay in 320 mode)
Double Dragon V - The Shadow Falls
Double Dribble - The Playoff Edition
ESPN Baseball Tonight
ESPN National Hockey Night
ESPN Speed World
ESPN Sunday Night NFL
Exile ................................................(Sega logo in 320 mode)
F-117 Night Storm ....................................(EA logo in 320 mode)
Fatal Fury 2 .........................................(Sega & Takara logos in 320 mode)
Fatal Fury ...........................................(Sega, Takara, & title screen in 320 mode)
Fighting Masters .....................................(all except story & main gameplay in 320 mode)
Flashback - The Quest for Identity
Flicky
Foreman for Real
Formula One ..........................................(all except main gameplay in 320 mode)
Fun 'n' Games ........................................(Sega logo in 320 mode)
FZ Senki Axis ~ Final Zone ...........................(Sega logo in 320 mode)
Garry Kitchen's Super Battletank - War in the Gulf
Gemfire
Genghis Khan II - Clan of the Grey Wolf
George Foreman's KO Boxing
G-LOC Air Battle .....................................(all except title & main gameplay in 320 mode)
Goofy's Hysterical History Tour
Great Circus Mystery Starring Mickey & Minnie, The ...(Sega logo in 320 mode)
Great Waldo Search, The
Growl ................................................(Sega logo in 320 mode)
Hook .................................................(Sega logo in 320 mode)
Insector X ...........................................(Sega logo in 320 mode)
Jammit ...............................................(Sega logo in 320 mode)
Kawasaki Superbike Challenge .........................(all except main gameplay in 320 mode)
King Salmon - The Big Catch ..........................(Sega logo in 320 mode)
Krusty's Super Fun House
Last Action Hero
Lawnmower Man, The ...................................(Time Warner logo in 320 mode)
Lemmings .............................................(all except main gameplay in 320 mode)
Lethal Enforcers
Lethal Enforcers II - Gun Fighters
LHX Attack Chopper
Liberty or Death
Lotus II .............................................(EA logo in 320 mode)
Lotus Turbo Challenge ................................(EA logo in 320 mode)
Mary Shelley's Frankenstein
Mega Bomberman .......................................(Sega logo in 320 mode)
Mick & Mack as the Global Gladiators
Mickey's Ultimate Challenge
Micro Machines .......................................(Codemasters screen in 320 mode)
Midnight Resistance ..................................(Sega logo in 320 mode)
Mighty Morphin Power Rangers
Miracle Piano Teaching System, The ...................(all except music menu & gameplay in 320 mode)
Monopoly .............................................(Sega logo in 320 mode)
Monster World IV .....................................(title screen in 320 mode)
Ms. Pac-Man ..........................................(all except main gameplay in 320 mode)
Muhammad Ali Heavyweight Boxing ......................(logos in 320 mode)
NBA All-Star Challenge
NCAA Final Four Basketball
NCAA Football ........................................(Sega logo in 320 mode)
Newman Haas Indy Car Featuring Nigel Mansell
NHL 94 ...............................................(all except title, menu, & gameplay in 320 mode)
NHL 95 ...............................................(all except title & gameplay in 320 mode)
NHL 96 ...............................................(all except main gameplay in 320 mode)
NHL 97 ...............................................(all except title & gameplay in 320 mode)
NHL 98 ...............................................(all except title & gameplay in 320 mode)
NHL Hockey ...........................................(all except title & gameplay in 320 mode)
NHLPA Hockey 93 ......................................(all except title, menu, & gameplay in 320 mode)
Nigel Mansell's World Championship Racing
No Escape
Nobunaga's Ambition
Operation Europe - Path to Victory 1939-45
Out of this World
Outlander ............................................(Mindscape logo & title screen in 320 mode)
Outrun 2019 ..........................................(logos, title, & options in 320 mode)
P.T.O. - Pacific Theater of Operations
Pac-Attack ...........................................(Sega logo in 320 mode)
Pac-Man 2 - The New Adventures .......................(Sega logo & title screen in 320 mode)
Pat Riley Basketball .................................(title, menus, dunks, and jump-balls in 320 mode)
Pele! ................................................(title and menus in 320 mode)
Phelios
Pink Goes to Hollywood ...............................(game start & options menu in 320 mode)
Powerball ............................................(title and menus in 320 mode)
Primal Rage ..........................................(title, menus, and character select in 320 mode)
Pro Quarterback ......................................(Sega logo in 320 mode)
Radical Rex
Roger Clemens' MVP Baseball ..........................(Sega logo in 320 mode)
Romance of the Three Kingdoms II
Romance of the Three Kingdoms III
Saturday Night Slammasters ...........................(Sega logo in 320 mode)
Scooby-Doo Mystery ...................................(initial title screen in 320 mode)
SeaQuest DSV .........................................(title screen in 320 mode)
Sesame Street Counting Cafe
Shadow of the Beast II ...............................(logos, title screen, & menu in 320 mode)
Shining Force ........................................(Sega logo in 320 mode)
Shining Force II .....................................(Sega logo in 320 mode)
Shining in the Darkness ..............................(Sega logo & name entry in 320 mode)
Simpsons, the - Bart's Nightmare .....................(Sega logo in 320 mode)
Sol-Deace ............................................(Sega logo in 320 mode)
Spider-Man Venom - Maximum Carnage
Spide-Man-X-Men in Arcade's Revenge
Spiritual Warfare
Splatterhouse 3 ......................................(logos, titles, intros, & cutscenes in 320 mode)
Star Trek - TNG - Echoes from the Past
Street Fighter II - Special Champion Edition .........(Sega logo in 320 mode)
Sunset Riders ........................................(Sega logo in 320 mode)
Super Battleship
Super Monaco GP ......................................(all except main gameplay is in 320 mode)
Super Street Fighter II ..............................(Sega logo in 320 mode)
Super Volley Ball
Syd of Valis
T2 - Terminator 2 - Judgment Day .....................(copyright screen in 320 mode)
Task Force Harrier EX ................................(Sega logo in 320 mode)
Tecmo Super Baseball .................................(Sega logo and some menus in 320 mode)
Tecmo Super Bowl .....................................(Sega logo and some menus in 320 mode)
Tecmo Super Hockey ...................................(Sega logo in 320 mode)
Tecmo Super NBA Basketball
Teenage Mutant Ninja Turtles - The Hyperstone Heist ..(Sega logo in 320 mode)
Test Drive II - The Duel .............................(all except main gameplay is in 320 mode)
Tick, The
Tom and Jerry - Frantic Antics
Top Gear 2 ...........................................(Sega logo, title screen + menu in 320 mode)
Toys
True Lies
Twin Cobra - Desert Attack Helicopter
Ultimate QIX .........................................(Sega logo in 320 mode)
Uncharted Waters
Uncharted Waters: New Horizons .......................(Sega logo in 320 mode)
Valis ................................................(Sega logo in 320 mode)
Valis III ............................................(Sega logo in 320 mode)
Venom . Spider-Man - Separation Anxiety ..............(Sega logo & copyright screen in 320 mode)
Viewpoint
Virtua Racing
Virtual Bart .........................................(Sega logo in 320 mode)
WarpSpeed
Wayne's World
WeaponLord
Wheel of Fortune .....................................(Sega logo, copyright, & title intro in 320 mode)
Wonder Boy in Monster World
WWF Raw ..............................................(Sega logo in 320 mode)
WWF Royal Rumble
WWF Super Wrestlemania
WWF Wrestlemania - The Arcade Game ...................(Sega logo in 320 mode)
Zoom! ................................................(Sega logo in 320 mode)