Organising your Library

3 categories:
Games
Finished
Boring

I choose the games to play randomly.

I tried so many ways to organize but most of then didn't work out.
Categories I had though all the phases: completed (not100% / no ach), 100%, trash, HOGs (mostly because they could be done relatively fast) and some promoted category for games I want/should/ am playing.
Tried depressurizer, but to be honest it's close to useless for me, lorenzostanco.com does a way better job at selecting a game based on positive/negative tag searches if I want to find a game based on criterias, and I know my games at least to the level of the main genre-categories of depressurizer add nothing to it.
I had numerous extra categories over the past 1-2 year - actual games, soon to be played, short games to play but I just kept throwing games into it but still mostly forgeting about them. So I tried a newish way recently: uninstalled ~100 out of 170 games, and started sorting them into played now/close future (all installed), very good games I shouldn't forget about (not installed) and I kept the extra mostly because savegames and such. For me too many installed games just make the choice harder, so I try to reduce their numbers, and it seems to work nicely - otherwise I'm like a toddler in a candy store - I want dis! and dis! and dis! *installs 15 games then play 1 of them in the next 3 months*

I really wish people could add estimated playtime to steam game son the store just like tags.

I'd love to organise by playtime.
Sometimes I want to play a really short game, sometimes I want to immerse myself in a sprawling, lengthy narrative or rpg game.

I realise it would be difficult as it's completely subjective. And people would probably start buying based on it, so games might artificially lengthen, but I just wish there was some way to organise by it :P

You could try arranging them via Publisher like Activision games, Blizzard games,THQ games, Rockstar games, EA games and so on.

Well, there's the default "Games" where my installed giveaway games go, "Games+" for single-player games that I like (for some reasons, I don't want to use favorite), "Completed" for those giveaway games where I got all achievement/cards, "Completed+" which is like completed tag but those that belong from Games+, "Alpha/Beta" for those alpha/beta, "DLC/Etc." for stuffs like the Starbound Unstable, PPU puzzle packs, etc., and "Multiplayer/Online".

My categories:
Favorites
Forced play
Should play
Could play
Try it
Games [Where all finished games or those with 0 interest end up]

By achievements:

Have achievements
Don't have achievements
100% completed games

I've organized my library by publishers

mine are:
Completed
Trash
Games