1.Silent Hill 2(By far my fave. THE prime example of what the gaming industry can achive.)
2.MGS1 (Before the series started to become stupid, possibly the most memorable game I have played.)
3.Hitman Blood Money (The replay value is amazing, a perfect example of non-linear gameplay without a vast or sandbox enviorment.)
4.Portal (Innovitive, enjoyable, funny, fast-paced, solid gameplay... this list goes on.)
5.Klonoa (Very uniqe gameplay that never tires, a cult classic.)