Games like Open The Gates!
Games like Open The Gates! include Stronghold Crusader HD (2012), Age of Empires III: Definitive Edition, Becastled, Stronghold: Definitive Edition, and Stronghold Crusader: Definitive Edition. We matched them by the tags players give Open The Gates! on Steam (RTS, Base Building, Strategy, Real Time Tactics, and Military): closest matches first, and among equally close ones the better-known games.

Stronghold Crusader HD (2012)
Shared: Military · Real Time Tactics · Base Building

Age of Empires III: Definitive Edition
Shared: Base Building · RTS · Strategy

Becastled
Shared: Base Building · Strategy · RTS

Stronghold: Definitive Edition
Shared: Strategy · Real Time Tactics · RTS

Stronghold Crusader: Definitive Edition
Shared: Strategy · Real Time Tactics · City Builder

Planetary Annihilation: TITANS
Shared: RTS · Strategy · Base Building

Manor Lords
Shared: Strategy · Base Building · City Builder

Stronghold HD (2012)
Shared: Real Time Tactics · City Builder · Building

Stronghold: Warlords
Shared: Real Time Tactics · City Builder · Building

Prison Architect
Shared: Base Building · Building · Strategy

Men of War: Assault Squad 2
Shared: Strategy · RTS · War

Total War: WARHAMMER III
Shared: Strategy · RTS · Real Time Tactics

Company of Heroes 2
Shared: RTS · Strategy · Military

Stronghold 2: Steam Edition
Shared: Real Time Tactics · City Builder · Building

Farthest Frontier
Shared: Strategy · Building · City Builder

Total War: THREE KINGDOMS
Shared: Strategy · RTS · War

Age of Empires II (Retired)
Shared: RTS · Strategy · Base Building

Kingdom Two Crowns
Shared: Base Building · Building · City Builder

Workers & Resources: Soviet Republic
Shared: Strategy · Base Building · City Builder

Call to Arms - Gates of Hell: Ostfront
Shared: Strategy · RTS · Real Time Tactics

They Are Billions
Shared: Base Building · Strategy · RTS

Frostpunk
Shared: Strategy · City Builder · Base Building

Against the Storm
Shared: Strategy · Base Building · City Builder

WARNO
Shared: RTS · Real Time Tactics · Military