Summon Night: Swordcraft Story 1 and 2.
I have absolutely seen NO ONE play it before, and it was an absolutely brilliant game. Amazing graphics, great gameplay and character design, and an engaging and memorable story. Sadly, Atlus shut the franchise down, making me cry buckets of tears when they announced it.
Arguably the greatest space adventure game + RPG ever back in 2001; uncomplicated, addictive and simply beautiful in so many ways. Even today I'd say it's one of the best space titles out there, I was so gutted when Freelancer 2 was cancelled.
Another special mention: Initial D: Special Stage (PS2)
Granted this was only ever released in Japan and SE-Asian countries, but it was so ball-crackingly AWESOME that I personally imported a Japanese PS2 just to play it.
Giants: Citizen Kabuto
System Shock 2
The Curse of Monkey Island
Tie Fighter (obviously people have, and it's a classic, but I kinda doubt that the majority of people on here did)
Little Big Adventure 2
Baldur's Gate (same kinda case as TF)
There's loads of others. I guess I was lucky being the age I was during the mid/late 90s and early 2000s. Because that was definitely the greatest period of all time for videogames.