1998 - Half-Life 1 released, still among my top favorites. (This was the game that inspired me to pursue game development as a career choice. About to transfer to Devry to finish up with a bachelors."
After that would have to be the Duke Nukem series. -- I enjoyed both the 3D and 2D versions very well.
http://mac.softpedia.com/screenshots/9-771_2.png
http://img408.imageshack.us/img408/1174/duke24tb8.gif
ooh, ooh, ooh, Almost forgot about Star Wars: Dark Forces 2: Jedi Knight. Was a great game I really enjoyed from 1998.
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Before I got a job, there weren't many pc games I got to play, primarily my parents are money conscious, so I'd only get to play games my father had enjoyed. Anytime before 2001 was a hard time for me to get games.
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Added some pic links

