I have had Fallout: New Vegas in my account for years. I had to have downloaded it about 2-3 times by now and never actually played it.

Batman: Arkham City.
Asylum and Alice: Madness Returns were on it for years though.. Probably others I've forgotten about, too, thanks to a backlog of 78 games.

What? Why wouldn't you play Bioshock...the best PC game in history?

The Witcher 2, i keep telling myself i will start to play it soon, but... there is always something new to play... D:

Lots of games. Often times, I will start a game, not feel in the mood to play it, and uninstall it. That has happened with Bioshock Inifinite, Far Cry Blood Dragon, Hitman Absolute (played a couple hrs i think), and Tomb Raider. I will more than likely go back and beat these games though. I recently did this with Alpha Protocol (bought it in like 2012, installed it immediately, didn't feel it, uninstalled it, recently reinstalled it a few weeks ago, and just finished it.). Alpha Protocol is a great game.

Most of games I play I play them on and off, hopping that i'll finish all the games I own one day, though I doubt :P

All of the games I have been putting off are because I can't run them, too long to download, or both. It's usually both.

GTA V, Wasteland 2 and Shadowfall Dragonrun are all high on my list, but I just never seem to get around to them.

many: fallout 3 (won here), fallout nv, witcher 1 (won here) and 2, skyrim, civV, mass effect 1 and 2, dragon age 1 and 2, amalur, far cry 3, half life series and some more. all of them are time sinks and i don't see in the next future that i have enough spare time to even touch them.

Games i would really like to play but can't seem to get myself playing them:
Amnesia
Bioshock 1&2
Fallout New Vegas (26 hours, still not finished & haven't started it since June 2014 :/)
Half Life 2 & Episode 1&2 (at least i played the original)
Hitman Series (only played Blood Money and a bit of Absolution)
Overlord 2
Spec Ops: The line (played for a few hours but never finished)
System Shock 2
The Witcher 1
Thief Gold

fallout 3 and new Vegas (but i don't like NV that much, so thats kinda why)
Borderlands 2
Orcs must die 1 and 2 (bought the bundle when it was on sale, only got a few levels into the first one before the orcs outsmarted me)
and trine 2
honestly not as bad as i expected, i'll probably get around to them later (but not NV, don't know why i don't like it)

Like most of you, I have tons of games in my backlog, but the one I feel worst about is Skyrim. Dragon Age: Origins is a close second.

I tried so many times to finish LIONHEART, but alaways stopped it at the beginning or half - there will be a day that I'll finally finish it !

dead island riptide, installed it 2 years ago. and yet its still installed on my computer and i never played it.

i cant bring myself to playing it or uninstalling it

Talking PC Games Stranded Deep and The Walking Dead: Survival Instinct.
On the 360 Eternal Sonata (for a few years now!), Dead Space 2 and Alan Wake.

Big list...
Witcher 1, Witcher 2, Witcher 3 (got as far as 2nd chapter in Witcher 1 so far - but put on hold to play Pillars of Eternity)
Dragon Age: Origins (got about 1/2 way through then got distracted)
Morrowind, Obsidian, SKyrim (Started Morrowind then got distracted, started Skyrim then got Distracted)
BioShock 1, 2, Infinite (Played the demo of Bioshock 1, but have never gotten round to playing the games)
FarCry 2 & 3 (Finished FarCry 1, and about 1/2 way through FarCry 2, but got distracted)
Batman: Arkham games
S.T.A.L.K.E.R. Games
Metro 2033 & Metro Last Lights (Started Metro 2033 (about 30 minutes playing) then got distracted)
Borderlands 1 & 2
Crysis 2
Age of Empires 3
Tropico 1, 2, 3, 4
Anno 2070
Overlord 2
Deus Ex games
Rome Total War
Port Royale 2
Various Warhammer 40,000 games (have completed Dark Crusade)
Stronghold 3
Risen
Europa Universalis IV
Fallout 3 & Fallout New Vegas
Total War: SHOGUN 2
Just Cause, Just Cause 2
Various Thief games (the old ones and the new one - got a few quests into the new one and the old one)
Various Hitman games
Crusader Kings II
Empire: Total War
Krater
Cities Skylines
Don't Starve (played on free weekend, and purchased game, then have not played since)
Left 4 Dead 2 (Played #1, and have never gotten round to playing #2)
Sniper Elite V2
Various King's Bounty games
7,62 High Calibre
Various Red Faction games (have completed first game)
Patrician IV
Supreme Commander 1 & 2
Warlock - Master of the Arcane
Various X3 games (completed X2)
Cities XL 2011
Serious Sam 3: BFE
Magicka
StarDrive 1 & 2
Various Tomb Raider games
Stealth Bastard Deluxe
The Banner Saga
Euro Truck Simulator 2
Saints Row 2, 3, 4
Strike Suit Zero
Company of Heroes (got about 1/2 way through then got distracted)
Roller Coaster Tycoon 3 Platinum (played #1 and #2 alot)
Torchlight 2 (completed Torchlight 1)
Sang-Froid - Tale of Werewolves
The Incredible Adventures of Van Helsing 1 & 2
War for the Owerworld
How to Survive
Two Worlds 1 & 2 (got about 1/2 way through Two Worlds 1 before getting distracted)
Grand Theft Auto 3 & 4 (Haven't even started them)
Battlefield 2 (never even started the game up)
Various Tom Clancy Splinter Cell games
SpellForce 1 & 2 (completed first mission in SpellForce 1 before being distracted)
Arma II
Various Cossacks games
Darksiders 1 & 2
Fear 1, 2, and 3
Fight the Dragon
Game of THrones
Legends of Grimrock 1 & 2
Middle-earth: Shadow of Mordor
and hundreds of other games that are not worth mentioning.

If PS3 games count, probably Mercenaries II.

I was about to beat it, and my cousin "Accidentally" erased my save files.

EDIT: Also, Long Live The Queen.

Uhm ... basically everything I haven't beaten yet XD

Procrastination: Buying an XBOX 360 and some games shortly after it came out and never getting around to opening the box.

Mafia 2 (GMG freebie from 3 years ago?)