Somebody gifted me a code for Saints row 2 last week (This was the first time I have gotten something like this as a gift) but the game is still not on my library after one week. What is the issue with this and Will I ever get the game or not?

If you entered the code and it was (still) valid, the game should have shown up in your library by now.

Regarding your two questions at the end: how is any of us customers supposed to know?

Contact support. Wait a few weeks. Have your issue resolved - or not, depending on what exactly the problem is.

This is not always the case. I am pretty sure if mutiple people enter the same code in a small window of time they wil all see the game as redeemed successfully but only the first will get it. I assume he wasn't the first one to redeem the code unless it was given personally by someone(or via the keyshare giveaways they use on reddit for example)

On the GOG site itself, make sure that you go to https://www.gog.com/en/redeem and redeem your code there until it appears in your account.

What about the words "still valid" didn't you understand?
If this should indeed be a case of "several people claiming the same key at the same time", and he wasn't the first one to do so, the key was not valid anymore.

The problem is that meanwhile the server is processing the code, several people receive the generic message if they redeem the code. I know because i had the same with other public codes.

Offtopic, but am I the only one weirded out about a month (2, if your genereous) old profile having 145 games in its profile? :S

Not that there's anything wrong with purchasing that many games in one go - to each his own - but I struggle to understand the logic... most games take days to months to complete - so why on earth would buy on average 4 every single day?!

I kinda understand not wishing to miss out on discounts, but come one...

Quite possible they was deep discounts and/or games they really wanted drm-free .. for example I in my first few months here went on a buying spree of games that was on sale I really wanted .. and I can't deny I keep that up monthly for awhile spending my personally set aside monthly allotment for entertainment till I basically largely depleted the gamess I wanted drm-free and/or get the games I had on console or Steam already to migrate over here as much as I can.. still do every once and awhile when a a large chunk of games that I have waited for a drm-free release show up here ..

I still also buy alot here but I can now go months with barely buying anything here now .. till games I have wanted to pop here well pop so long as they are cheap enough .. Granted afew times I bought games full price

<Collecting Mode Active>

https://www.gog.com/user/refresh

Do you know who gave you the key and where they got it from?

If they got it from GOG you can ask them, because it tells in their library who redeemed it.