Tell gog maybe and inform them? Maybe they can track down who asked for the reset?

You might want to take this as a sign it's time to change your password anyway. But do it from your account page rather than the email link.

Either way you should change your password, just to be safe.

What e-mail was the message sent from?

Came from here: do_not_reply@gog.com

And the link to change the password starts with: https://www.gog.com/?passRes=

So it looks like a real password reset request.

I'd change your email password......if someone did this they might think they can get into your email(for some reason...maybe they think they have the skill or know your password) and use that link. Change your email password pronto...that's my advice.

I agree; definitely do that as well, gyokzoli. Better safe than sorry.

Maybe you left some PC while logged-in (like office PC)?

Why bother? It is a lot easier to find the games floating on the net than hacking somebodys system...

Well, at least gyokzoli has now an excellent excuse to start all those "I like big buts and I cannot lie" threads without scrutiny ;-P

Someone might want to use their account to make them look bad, or for some other purpose(Like reading their PMs for personal info, etc.)?

Change the passwords of all your mail accounts. There's a chance that one of your accounts has been compromised and that an attacker is now checking which other passwords he can retrieve (or get control over) through this leak.

Definitely ask GOG if they can trace the IP from which the request originated. It probably won't lead to the culprit (it's not hard to cover one's tracks), but it can help verifying that something fishy is going on. Or perhaps it was just a malfunction in GOG's mailbot, or there may actually be a user with a similar name who accidentally typed yours while trying to log in. In any case, these are questions that GOG support should be able to answer.

Also, be wary of possible security breaches on other platforms. Usually, hackers don't try such things unless they already have some leverage somewhere.

The only two things I can think of as to the causations of this situation are:

1) GOG actually did send it and sent it by mistake
2) He is being "phished" where the people are hoping he reuses his GOG password on other, more important sites

I'm actually leaning towards 1), but it is better to be safe than sorry in these instances and simply change the passwords, but by going through GOG's page rather than the link in the suspicious e-mail and his e-mail password through his e-mail provider's portal. Annoying but easy to do.
I think more likely (if it is a phishing attempt) is to obtain the password and hope he reused in a more important site.

On GOG, you log in with your e-mail.

EDIT: And I just tried, the actual password reset e-mail indeed arives from do-not-reply@gog.com and the text is the same. So it's probably not phishing.

Every automated email I get from Gog is from that address.

Edit: Oops, almost. Newsletters are from newsletter@gog.com