I agree with @GazzaGarratt it's hard to pick, the insane amount of games to choose from.
I agree Tomb Raider was great as well.
Metal Gear Solid was something else at the time.
Honourable mentions to Tenchu and the original Grand Theft Auto as well.
Goldeneye, Medal of honour and Age of Empires 2, like J4MES and Phil mentioned also.
Now I know this is slightly further ahead, but on the year 2000 alone we had.
Tony Hawks 2, Hitman 1 and the first Splinter Cell!
Splinter cells graphics blew everything out of the water at the time. I remember it so well. It was incredible.