Resident Evil Series
Forza 3 + 4
Gears of war Series
Call of Duty Series
Grand theft auto Series
Crysis Series
Witcher 2
Skyrim
Tekken 2
Vampire: The masquerade bloodlines
Test Drive Unlimited 2
I have many more but those are the ones I would never sell.
Gothic Universe
Witcher 1 and 2
World in Conflict Collectors Edition
Company of Heroes
Risen
Heroes of Might and Magic 1 - 6
Borderlands
Nox
Darksiders Hellbook Edition
Skyrim
I've got some classics sitting on the shelf as originals that I could never replace. Among them are the Discworld games, the Gabriel Knight games, Tex Murphy 3, 4 and 5, an original The Longest Journey... My Dreamfall CE is holy to me, so is the Warcraft 3 CE from back in the day. Generally anything that is CE or Limited Edition will be with me til the day I die.
I usually collect my games for the current console version, but i must say at the moment non of my games are being let go of. There was only two i hated and that was Shaun White Snowboarding and Mirror's Edge, that i got rid of immediately.
But if i must name a few:
Uncharted Series
Heavy Rain
God of War Series
Infamous Seires
Assassins Creed Series
Rachet and Clank Series