Unreal (1998) on release was mindblowing and I was one of the few lucky ones to experience it then with 3D acceleration (3dfx Voodoo 2), but it scales poorly on modern monitors and looks blocky as hell today. It is funny that Half-Life and Thief look better than Unreal today thanks to official and unofficial patches and the visual style and environments of those games. But I will never forget walking out of Vortex Rikers for the first time into what felt like a living and breathing alien world in Unreal. Console gamers had to wait at least a few years to experience something like that. Unreal could have been released on PS2/Xbox but with much lower resolution and with frequent and long loading times. Unreal was the Crysis of the 90s.
Deus Ex (2000) - a game that pushes the boundaries of what the video game medium is capable of to a degree unmatched to this very day.
