Oddworld: Abe's Exoddus

Inspired game: R.E.L.I.V.E.

Media: Oddworld: Abe's Exoddus

Oddworld: Abe's Oddysee

Inspired game: R.E.L.I.V.E.

Media: Oddworld: Abe's Oddysee

OGRE

Inspired game: Alimer

Old School RuneScape

Inspired game: RuneLite

Media: Old School RuneScape

Omega Race

Inspired games: StarMines: The Next Generation, Torrega Race

Media: Omega Race

One Must Fall: 2097

Inspired game: OpenOMF

Media: One Must Fall: 2097

Open Dune

Inspired game: Dune Dynasty

OpenMW

Inspired game: TES3MP

Osu! Tatakae! Ouendan

Inspired games: opsu!, osu!

Media: Osu! Tatakae! Ouendan

Oubliette

Inspired game: Liberal Crime Squad

Out Run

Inspired game: Cannonball

Media: Out Run

Outlaws

Inspired games: The Force Engine, XL Engine

Outpost

Inspired game: Outpost HD

Overgrowth

Inspired game: Overgrowth

Oxyd

Inspired game: Enigma

Media: Oxyd