Enter an interstellar odyssey in Halo: Combat Evolved, the pioneering first entry in the iconic franchise. Assume the role of Master Chief, a legendary supersoldier, against the relentless Covenant threat. Engage in exhilarating battles across alien landscapes, armed with cutting-edge weaponry. With its compelling storyline, immersive multiplayer, and innovative gameplay, Halo: Combat Evolved delivers an unforgettable sci-fi experience. Stand ready to defend humanity among the stars.

Wikipedia: Halo: Combat Evolved

The player again picks up the crowbar of research scientist Gordon Freeman, who finds himself on an alien-infested Earth being picked to the bone, its resources depleted, its populace dwindling. Freeman is thrust into the unenviable role of rescuing the world from the wrong he unleashed back at Black Mesa. And a lot of people he cares about are counting on him.

Wikipedia: Half Life 2

Dive into the heart of the conflict in Halo 2, the highly anticipated sequel to the iconic franchise. Reprise your role as Master Chief, the legendary supersoldier, and engage in an epic battle against the Covenant forces. Experience intense multiplayer action across a variety of dynamic maps, each offering strategic opportunities and adrenaline-fueled combat. With its gripping storyline, expanded gameplay mechanics, and stunning graphics, Halo 2 set a new standard for sci-fi gaming.

Wikipedia: Halo 2