1) Zork. This was my first computer game. My first PC was a dual (5inch) floppy with 640k(!) of memory. It was a text based game. "You are in a room with a table and two doors" type: exit room. "the doors are locked" type unlock doors; "you don't have a key"...etc
2) Grim Fandango. Spent so many hours in this amazing world. Made by the good folks at Lucas Arts the art deco time period and artwork in the game is stunning. Use arrow keys to move around and action keys to do stuff like pick up, open door...etc. When interacting with other characters there is a choice of things to say and you chose one and it affects the outcome. A fantastic experience.
3) Unreal Tournament. Never was much of a Quake fan. I always preferred the punch of Unreal Tournament's weapons. Not too much thinking just fire and laugh.
4) Serious Sam. Serious Sam fans will smile at my skype name (under my avatar) as being based loosely on one of Sam's favourite sayings "Sam I am". Sam's not only awesome but he's funny too. Aim of the game - kill all monsters (some of which are REALLY creative) with enourmously overpowered weapons while cracking wise.
5) Race Driver. Based on the Australian V8 Supercars franchise I drove most of the world's famous tracks in all sorts of classes using my Logitech feedback steering wheel and pedals.
Reminisce about some of the old games you loved.