Games like Fallout: New Vegas
Games like Fallout: New Vegas include Fallout 4, S.T.A.L.K.E.R. 2: Heart of Chornobyl - Standard Edition, Cyberpunk 2077, Fallout 3, and Metro Exodus. We matched them by the tags players give Fallout: New Vegas on Steam (Open World, RPG, Post-apocalyptic, Singleplayer, and Moddable): closest matches first, and among equally close ones the better-known games.

Fallout 4
Shared: Open World · Post-apocalyptic · Singleplayer

S.T.A.L.K.E.R. 2: Heart of Chornobyl - Standard Edition
Shared: Open World · Post-apocalyptic · Singleplayer

Cyberpunk 2077
Shared: Open World · RPG · Singleplayer

Fallout 3
Shared: Open World · RPG · Post-apocalyptic

Metro Exodus
Shared: Post-apocalyptic · Open World · Singleplayer

Starfield
Shared: Open World · RPG · Singleplayer

The Elder Scrolls IV: Oblivion® Game of the Year Edition (2009)
Shared: Open World · RPG · Singleplayer

The Witcher 3: Wild Hunt — Remastered
Shared: Open World · RPG · Story Rich

Hogwarts Legacy
Shared: Open World · Singleplayer · RPG

The Elder Scrolls IV: Oblivion Remastered
Shared: Open World · RPG · Singleplayer

Red Dead Redemption 2
Shared: Open World · Story Rich · Singleplayer

Kingdom Come: Deliverance II
Shared: RPG · Open World · Singleplayer

Tainted Grail: The Fall of Avalon
Shared: Open World · RPG · Singleplayer

BioShock Infinite
Shared: Singleplayer · RPG · Action

Terminator: Resistance
Shared: Post-apocalyptic · Open World · Singleplayer

Kingdom Come: Deliverance
Shared: RPG · Open World · Singleplayer

Biomutant
Shared: Open World · RPG · Singleplayer

Crimson Desert Enhanced
Shared: Open World · Singleplayer · Exploration

God of War
Shared: Singleplayer · Story Rich · Action

The Elder Scrolls III: Morrowind Game of the Year Edition
Shared: Open World · RPG · Moddable

METRO Last Light Redux
Shared: Post-apocalyptic · Story Rich · Singleplayer

METRO 2033 Redux
Shared: Post-apocalyptic · Story Rich · Singleplayer

Far Cry® New Dawn
Shared: Open World · Post-apocalyptic · Action

The Outer Worlds 2
Shared: RPG · Open World · Singleplayer