What you're asking strikes true for console gaming too, very few have been released that were really good, and of the titles you've noted they are single player console primary games. To me the PC holds it own for very competitive online gaming, MMORPGS, first call for indie games, strategy games and niche games/sims.
I'm personally going to say Counter Strike Global Offensive - this added the competitive nature that CS:S was lacking and for that it will get hours of gameplay, more so than any single player game I'll own. There is a gimmick in getting fancy weapon skins but this at least rewards for putting hours in.
Insurgency and Rising Storm also fill a niche not found on a consoles which whilst frustratingly hard have become a firm favourite of mine for the sheer unique experiences they offer alone.