No Man's Sky. Tried to like it, even after the update but it's just meh.
Over 1000 games in my library and only completed about 10 of them. Lots at zero hours though they're mostly bundles fillers.
Games that I purposefully bought that were in fact a waste of my money and not part of a bundle.
Middle Earth: Shadow of Mordor - unplayed
Amnesia the dark decent - unplayed
Civ 5 - 1.5 hours
Call of Duty 4 - 0.9 hours
Max Payne 3 - 0.7 hours
Arma 2 - 0.2 hours
GTA V for me. Under 10 hours, I got bored and uninstalled it.
On the flip side, after three attempts, The Witched 3 is probably my all time greatest gaming experience.
About 90% of all my games have only been started to get the steam trading cards data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
Must admit, Ive got a bit of a bad habit of buying a game with all the intentions of playing them and then never getting around to it.Looking at my collection, I don't have many where ive played for more than 20 hours but i have finished quite a few.
That said, heres probably the ones I consider a bit of a waste based on time played v cost..
XCom 2
Mafia III
Castlevania Los 2
All COD games - COD 4 - to Present release*
American Truck
Mad Max
Neir Automata
*I've finished nearly all Cod games on other platforms, I just like to collect them on PC
Full price or Close to Full price (codes from GPUs at say £15 ) or Kickstartered or Pre-release games not played at all:
Dishonoured
Witcher 3
Dragon Age Inquestion
Borderlands 2
Divinity Original Sin
Broken Sword 5
Carmagedon
good chunck of mine have barely been played due to having so much to play on both pc and console.
I have found this steam sale rather poor this time round but sort of glad as I would have purchased some games and probably not play them for a while lol.
edit
just looked at my list
witcher 3 has 43 hours and i have only done half of the game. I think only another two games have a good run through and that is tomb raider and van helsing
I have 287 games in my GOG library, and the unevenness of that list is even more depressing reading. Maybe one in ten classic games actually play well if you avoid the nostalgia goggles.
OTOH there are many games I have really got my money's worth from, even if a lot of the 300 hours I have apparently played Baldur's Gate II must be due to having the game paused overnight to trigger the next realtime timer-based party interaction...
There's my Steam library: Steam Community :: HarryPothead :: Games
Pretty much 80% of my 300-odd games apparently have 0 hours playtime. I'm fairly sure that some of those tallies are totally wrong, Fallout 3 and Dishonored , for instance. There's games on that list I've played the hell out of but the hours just haven't been tallied.