|I'm kind of ashamed of the number of games I own but haven't actually played very much or at all despite wanting to. On several occasions, though, I have actually sat down, played through, and enjoyed games I originally got years ago, so I'm hoping that it's not in vain.
Just on Steam, there's Darksiders II, Dead Space, Mirror's Edge, Supreme Commander, Warhammer 40K: Dawn of War - Dark Crusade, and X-COM: UFO Defense that I haven't played even for a minute. There's also Dustforce and Hyper Light Drifter, which I've played for less than 30 minutes each. I could make a very large list if I just start listing games I haven't finished in general, though.
As for non-Steam games, there's AM2R, Catacomb Kids, Dungeon Keeper, Fallout 2, Gone Home, La-Mulana, Momodora 2, Nuclear Throne, Neverwinter Nights, Ruby & Majesty: Treasure Team, StarCraft II, and Uurnog. I also have a copy of Metroid Prime 2 that I got over a decade ago and spent probably less than an hour playing it that I would like to revisit someday.
Anyway, there are a bunch of other PC games I don't actually own that I'd be interested in playing. The main ones that come to mind, though, are the new Doom, Nier: Automata, Factorio, Iconoclasts, CrossCode, Sonic Mania, Cuphead, Songbringer, Hollow Knight, Caves of Qud, and Magic Wand.
I don't own any console more modern than a Wii, so I've really missed out on console gaming for the last several years. Despite that, I can't think of many console games I haven't played that I would to try. The main ones that come to mind, though, are Super Mario Odyssey, Breath of the Wild, Super Smash Bros. for the Wii U, Super Mario Maker, Journey, and Bloodborne.
In practice, I have less and less time to actually play video games and less and less motivation to dedicate my time to learning how to play (often lengthy) new video games. I'm much more likely to just play something I'm already familiar with or very short indie games these days. I'll probably never get around to playing a lot of these.