I'd be inclined to recommend an Xbox Series S or Series X for the exclusives Starfield, Quantum Break, Shadow Complex, the Halo series, and the Gears of War series. Other great sci-fi games available for Xbox (and other platforms) include The Outer Worlds, Prey (2017), Outer Wilds, No Man's Sky, Alien: Isolation, Mass Effect Legendary Edition, the XCom series, the Deus Ex series, the Bioshock series, Surviving Mars, Deliver Us The Moon, Deliver Us Mars, the Fallout series, the Dead Space series, Cyberpunk 2077, the Portal series, and many others. Note a number of these games are currently available on the Game Pass Ultimate subscription service for Xbox as well.