I have 580 games and no idea which one i should play

Play one of the Ys games, either I or Oath in Felghana.

Bioshocks!

I see you haven't finished Bad Rats. What are you waiting for?

I use this

http://steam-roulette.heroku.com/

Play XCOM: EU. I've been playing it a lot lately and I had forgotten how excellent it is.

The binding of Isaac, Beat hazard, BIT.TRIP RUNNER, Alan Wake, DayZ, Assassin's Creed 2, Bully, Chivalry, Killing Floor, Need For Speed, Portal 2, Sniper: Ghost warrior 2.

Edit: PUZZLE AGENT!!!!!!!!!!!!!!!!!!!!!!!!!!!! How can you have that game and not play it?!!

get on kotor 1 and 2

Use backloggery and the fortune cookie feature. Especially helpful if you have games outside of Steam as well.

Have friend withmore than 3500 games. Ask him :D

X2 , half life 2, fallout 2, world of goo

Aliens: Colonial Marines, I heard it's good :P

I have an idea for you: Oranize your games library into categories like "Single Player Only", "Co-Op and Single", "Games" (in Games there should be games that have single player and also multiplayer) and finally create a category named "History". Then start finishing the Single player only games that you like. After finishing a single player game, move it into the "History" category. Do that until the single player games are finished and their category is depleted. Then start finishing the single player campaign of the "Games" category that also have multiplayer.

I'm just playing games one by one starting from the top of the list and after I've finished them I move them to my "Done" category. Basically, go alphabetically!

Easy GTA IV. You won't want to play anything else once you get into it.

I play/finish games when I get them then buy new ones but I don't have many games o.o

You can use online random tool to generate a number between 1 to 580. Then you get the number, you can find the relevant game in your list.

Oh man, there're too many great games.
Try Binding of Issac or Thief Gold.

use this site

noob asking others which game he wants to play... PRO

If you haven't, try Trouble in Terrorist Town game mode (you have to have a source game, OR, go youtube and find a video to get the required texture pack)
I swear, if you manage to find a low latency (<100 ping) with enough people (>10 ppl), it's FUN AS HELL. I managed to spend a lot of hours without even realizing it. Such fun.

I'm going to suggest one that everyone above didn't mention. Start playing Thief series, and after finishing, play Dishonored, and then the new Thief which will be released next year. Oh, you already have Dishonored with 1.2 hours on record. You have only played for 1.2 OMG 1.2, ONLY 1.2!!! hours, I guess you'll never like Thief. So forget about it.

Payday 2? Been meaning to get that, how is the dlc? Only had it for 360 and never left beta. :(

modesty

Xorph - choose Jet Set Radio (!) a bunch of fun from the Dreamcast!

+maybe:

• Legend of Grimrock (!) (currently best dungeon crawler, with many good mods)

• Dark Messiah of Might & Magic (great fights with magic, male and ranged weapons)

• Penny Arcade's On the Rain-Slick Precipice of Darkness 3 (if you like funny indie games, its casual crpg)

• Crysis 2 (great "Fast and Furious" FPS, full of action)

• Lost Planet 1 and 2 (if you like arcade TPS)

• Bully: Scholarship Edition (one of a kind)

• Aliens: Colonial Marines (just try it, I had a good time with CM)