| Title | Year | Publisher | Serial | Rating |
| Obscure | 2004 | DreamCatcher Interactive | SLUS-20777 | 9.4 |
| Obscure: The Aftermath | 2007 | Ignition Entertainment | SLUS-21709 | 8.5 |
Odin Sphere  | 2007 | ATLUS | SLUS-21577 | 9.5 |
| Okage: Shadow King | 2001 | SCEA | SCUS-97129 | 8.2 |
| One Piece: Grand Adventure | 2006 | Namco Bandai Games America | SLUS-21435 | 9.6 |
| One Piece: Grand Battle | 2005 | Bandai | SLUS-20975 | 7.0 |
| One Piece: Pirates' Carnival | 2006 | Namco Bandai Games America | SLUS-21364 | 9.0 |
| Oni | 2000 | Rockstar Games | SLUS-20064 | 7.4 |
| Onimusha 2: Samurai's Destiny | 2002 | Capcom | SLUS-20393 | 9.0 |
| Onimusha 3: Demon Siege | 2004 | Capcom | SLUS-20694 | 9.1 |
| Onimusha: Blade Warriors | 2004 | Capcom | SLUS-20710 | 7.7 |
| Onimusha: Dawn of Dreams | 2006 | Capcom | SLUS-21180 | 7.7 |
| Onimusha: Warlords | 2001 | Capcom | SLUS-20018 | 8.9 |
| Ookami | 2006 | Capcom | SLUS-21115 | 9.6 |
| Open Season | 2006 | Ubisoft | SLUS-21467 | 7.0 |
| Operative, The: No One Lives Forever | 2002 | Sierra Entertainment | SLUS-20028 | 8.2 |
| Orphen: Scion of Sorcery | 2000 | Activision | SLUS-20011 | 8.3 |
| Outlaw Golf 2 | 2004 | Global Star Software | SLUS-21030 | 9.0 |
| Outlaw Tennis | 2005 | Global Star Software | SLUS-21190 | none |
| Outlaw Volleyball Remixed | 2005 | Global Star Software | SLUS-21049 | 8.7 |
| OutRun 2006: Coast 2 Coast | 2006 | Sega | SLUS-21274 | 10.0 |
