Answers:

1) About 40, almost all from bundles/package deals
2) I will likely never play 90% of my currently unplayed games as I already have played the games I wanted from the bundles.
3) Usually two games; one action game and one puzzle game
4) I try to play all games I start to completion or at least far enough that I feel that I am finished.

1.) 1000+, no idea how many exactly.
2.) "Random" aka it depends on the mood I'm in.
3.) Pretty much only ever one (currently none, unless you want to count playing Mahjong online as one).
4.) Yep, absolutely. There are very few exceptions to that rule and I can even name those. I do intend to finish them eventually, regardless of how long it's been since I touched them.

1) How many unplayed games do you currently have (GOG + non GOG)?

Totally I have 120 games.
28 finished
4 buggy, so I can not play them
7 games waiting for new GPU, currently I do not have enough horse power to play them
9 games I did not enjoy, so I stopped playing them
(rest is not completely unplayed; including 64 freebies)

2) How do you select a new game to play from the above?

This totally depends on my mood (from long term perspective)

3) How many games do you play concurrently?

Just one

4) Do you normally play games through to completion before moving on to another game?

Yes, unless I am dissapointed with the game. In this case I delete game and move on.
(in some cases I install more games and play each for hour or two to see what I prefer right now)
For long time I have Total Annihilation, but I do not play it, because it is too long (and although I like strategies, I love other genres more).

1) A lot. Mainly because I don't have a strong PC.

2) Any game that appeals me with gameplay or visual.

3) 1-2 games.

4) Yes.

1) Upwards of 200. I bought too many bundles, here and on humble. Also, if it's a long or involved game (for example, the Civilization series, or an in-depth RPG), I'll put it off and play something I already know half the time.

2) Mood, maybe I'll check through reviews as well. For example, I recently decided that I should play through the Awakening campaign of Dragon Age: Origins. No particular reason, but the reviews confirmed that it would be fun and not all that long.

3) 2-3, maybe. Into the Breach or FTL for quick sessions, and usually a big RPG or 4X game.

4) These days I do. I hate trying to come back to a game after months of not playing and figure out what's going on.

1. GOG: ~1700. Non-GOG: lol i dunno.

2. Browse the library until I find a tile with a picture I like best, start the download, go read about fan patches and shit, get tired, go play Sigmar's Garden instead.

3. ??? Only one, and maybe Fallen London in a browser window.

4. No, basically never.

1) Approximately.

2)I ask her.

3)Three of four.

4)NO

1) How many unplayed games do you currently have (GOG + non GOG)?
23 (About 10 of them I probably never will play because they don't match what I like to play these days, something I already knew when I bought them. I bought them because I liked how they look and what they seem to do and wanted to support the developers -full price or discount-.)

2) How do you select a new game to play from the above?
If I am not in the mood to continue one of the games I already started or play one from my "quick games" list, I pick the unplayed game that seems to match my current mood best. Or I want to play a specific unplayed game and do exactly that.

3) How many games do you play concurrently?
On a single day I play 1-3, sometimes 4 games, but not concurrently only ever one at a time. Usually one more "demanding" (= longer and/or "complicated", e.g. strategy/hard thinking/"number crunching") game and at least one other game from my "quick games" list to "shake my brain out" a bit at the end of my "game time" and/or in between sessions of this longer game.
Otherwise: I have about 30 games (? didn't count) installed right now. I play/continue/replay/start over any of them when I'm in the mood to do so.

4) Do you normally play games through to completion before moving on to another game?
No. I play games for fun and if a game isn't fun for me it's a waste of my time.
(I made an exception for Solstice because I liked the story and characters and wanted to see at least one ending before I quit. And I will probably pick it up again once I'm done being angry because I want to find out if there is a "good path".)
That also means, it is pointless to play a game I'm not in the mood for because to me this would be a chore not fun.

1) How many unplayed games do you currently have (GOG + non GOG)?
Dear lordy. There are just too many in the library to count. However, most are freebies from Humble that I may never touch.

2) How do you select a new game to play from the above?
I usually choose to play games I purchased 1st followed by games I've won from giveaways done by fellow goglodytes 2nd followed by freebies given away en masse from sites like Humble, Gog, and Steam 3rd. There's also a degree of "how badly I want to play it" so I may play something from a giveaway first over a purchased game if it's something I really really want to play.

3) How many games do you play concurrently?
2. I have one that I play on my big rig when I'm home and one that I play on phone or laptop when I'm not at home.

4) Do you normally play games through to completion before moving on to another game?
Yes...most of the time. The last time I didn't finish a game was in 2008 when I was playing Atlantis Evolution. The game was so bad I couldn't finish it. Since then I've played every game to completion before moving on to the next one.

1) Don`t know, really.
2) Well, I just browse thru my games and one moment it makes "Click" and I know what to play next.
3) Well, at least 3 or 4.
4) Nope. I do complete not much games, but I love to play them.

1) How many unplayed games do you currently have (GOG + non GOG)?
Roughly 500
2) How do you select a new game to play from the above?
I play the ones that look the coolest!
3) How many games do you play concurrently?
Roughly 11
4) Do you normally play games through to completion before moving on to another game?
No. About half the time I play until I am done with the game - rarely until the game itself thinks it has been finished. The other half of the time I play for a while and then uninstall to pick up again some day.

1. 6 on GOG (2 of them are InDev, played some earlier build & now waiting for the finished version). 0 games from my retail collection (played all of them through the years and still play from time to time).
2. It's mostly a matter of available free time (i'd start a cRPG when i know i'd be able to finish it) and mood.
3. Not counting the various racing/flight sims that are perpetually installed on my system and i'm playing on a near daily basis (there are six of them), i'd say one. Or two. Never of the same genre though.
4. Yes.

1. 277 unfinished and 171 unplayed. GOG only.

2. Mood 90%, 10% inspiration from others

3. Nowadays only 1, maybe 2.

4. Not anymore.

1. Depends on the definition of "unplayed". If you mean never touched and tried yet, maybe 15-20%? If you mean not played through, then probably 80-85%. The actual numbers I'd rather not say - yes, they're that high. ;P

2. I just go by whatever I feel like playing at the moment; when I have no clear idea of what that is, I browse through my collections and pick out a couple of games to try.

3. Also depends on the definition. But in any case, several.

4. No. I prefer "natural selection". I start several and see what I enjoy the most; if something really draws me in, I finish it automatically, because I want to, not because my rules tell me to. If something bores me, it's okay for me to abandon it.

1. I haven't bothered to count that.

2. Dartboarding or recommendations from peers.

3. Around 1, but I also tend towards nonform games that have rather open goals.

4. No. I tend to get distracted.