Morrowind GOTY (I know, pathetic - made it about 15 hours and stopped).
Lord of the Rings Online - have a lifetime subscription and never made it past level 32.
Gothic 3 - Never made it out of the area immediately around the starting village
Divinity 2: The Dragon Knight Saga - have never downloaded it after buying it. Supposed to be greatly improved over Ego Draconis (which I only played for about 20 hours)
The Witcher Enhanced Edition - I hear its great put I never got beyond the first little village
Sacred and Sacred 2 - Made it about ten levels or so with each.
Titan Quest and its expansion - I hear this is great, but only played a few hours.
Two Worlds II - played about 40 hours, but then Skyrim came out and now I'm scratching my head trying to remember the story.
I'm always looking at new PC hardware upgrades, but I could keep myself busy for a couple of years with these old games that run easily on my current system. /sigh. How the heck can I get motivated to get my money's worth out of them?