Sci-Fi

Sci-Fi themed games are games that are characteristic of science fiction literature; the narrative is dependent on the impact of scientific discoveries that do not yet exist in reality. Some games, such as those in the Half-Life series and Unreal series take place in a sci-fi universe that was created specifically for the purpose of the games. Others may take place in existing sci-fi universes, such as licensed Star Wars games. Common elements of sci-fi themed games include futuristic settings, high-tech items and weapons, and alien characters.

Earth 2150

Earth 2150 (and its EPs) is a sequel to Earth 2140. Eurasian Dynasty has launched nukes around the world. This has changed orbit of earth, now it's going to sun.

You, commander of ED, UCS (United Civilizated States) or LC (Lunar Corporation) , have to gather a lot of money and make an escape ship to Mars. The game was released in 2001.

Command & Conquer: Red Alert 3

Command & Conquer: Red Alert 3 is the sequel of Command & Conquer: Red Alert 2. The Soviets are almost dead, the Allies celebrate their victory.
In this hard time dr.Zelinsky invent a time machine. Similar to Einstein's one.
Premier Cherdenko and general Krukov are using device to delete Einstein (responsible for Allies technology advancement) from history and bring victory to motherland.
Trick works and USSR is strong again. However, there are unforeseen consequences.
The Empire of the Rising Sun is trying to conquer the world with their advanced technology and spirit of fight.

Darkest of Days

Darkest of Days is an FPS from 8Monkey Studios, published by Phantom EFX. The game is seperated from the average FPS game by using mainly the Civil War and World War 1 and its settings, two time periods not often depicted in action video games. Sometimes you will use period weapons which are slow and cumbersome, and then you will be granted a modern day weapon with which to cause havoc, which always feels very satisfying.

StarCraft

StarCraft is a military science fiction real-time strategy video game developed by Blizzard Entertainment. The first game of the StarCraft series was released for Microsoft Windows on 31 March 1998. The game has had its storyline adapted and expanded through a series of novels, the expansion pack StarCraft: Brood War and two authorized add-ons. The sequel, StarCraft II: Wings of Liberty, was released in July 2010.

Half-Life (Non-Steam)

Half-Life is a 1998 first-person shooter (FPS) game developed by Valve and published by Sierra Studios for Windows. It was Valve's debut product and the first game in the Half-Life series. Players assume the role of Gordon Freeman, a scientist who must escape the Black Mesa Research Facility after it is invaded by aliens. The gameplay consists of combat, exploration and puzzle-solving.

Star Wars: X-Wing Alliance

Star Wars: X-Wing Alliance or XWA is the sequel to both Star Wars: TIE Fighter and the multiplayer-focused X-Wing vs. TIE Fighter. XWA presents the story of the Azzameen family, a family of space traders. The player assumes the role of Ace Azzameen, the youngest of the Azzameen children.

Turok

This game is a FPS with a mix of stealth elements. And dinosaurs. Lots of dinosaurs. A whole lot. Certain events will trigger cinematic sequences that involve Turok executing his opponent in graphic fashion. Other events involve pressing button combinations to fight off an attack and survive. Crouch in the tall grass, break out the knife, and wait for the little dinos to wander by.

Battlefield 2142

Battlefield 2142 is a 2006 first-person shooter video game developed by DICE and published by Electronic Arts. It is the fourth game in the Battlefield series. Battlefield 2142 is set in 2142, depicting a war known as "The Cold War of the 22nd Century", in which two military superpowers – the European Union (EU) and Pan Asian Coalition (PAC) – battle for the remaining unfrozen land during a new ice age.

Source: Wikipedia

Defense Grid: The Awakening

Defense Grid is a 3D singleplayer tower defense game. You must construct defensive towers of various types on predetermined areas to get rid of incoming alien swarms before they reach your mainframe and run with its power cores.

The Chronicles of Riddick: Assault on Dark Athena

Chronicles of Riddick: Assault on Dark Athena is the sequel to Chronicles of Riddick: Escape From Butcher Bay from Starbreeze Studios in association with Vin Diesel's Tigon Studios. The game includes the original Butcher Bay game with enhanced visuals to match the sequel. Gameplay focuses on first-person stealth, melee combat and shooting, along with a strong focus on story, dialogue and cinematic moments. One of the most overlooked shooters in recent years, Dark Athena deserves a purchase from all FPS fans.