Haven't used Steam and don't plan to. 48 xxx games/VN (both completed and in development) is my entire “library”. How many games have I tried and quit? Didn't count. Since xxx games are not even remotely masterpieces, I save them in extremely rare cases. As a rule, I play them and throw them away.
397 games on steam. About half of them are MMO games or free games from giveaways. About 20% are old games that I played a long time ago, I just decided to buy them on sales. All these games, in most cases, I did not even install. I played the rest of the games and finished most of them.
If we are talking Steam I have played 59% 81/138, if we are talking AVNs...
20 - in progress
29 - next in queue
43 - waiting for update
100 appox - backlog
192 - total appox
Between the various consoles and game platforms, I have way to many to get through since most of them are 60+ hour games. Probably played most of them at least once to try them but only completed around 10% would be my guess.