I believe I am not alone in having felt that GOG’s game search options leave quite a bit to be desired. Having recently reduced my backlog to only a few hundred games, I decided I now had the time to stop sitting on my backside and do something about it (the search, not the backlog, nor the backside).
So I wrote my own search engine: MaGog.
Read its tutorial to learn how to use it and follow this thread to keep abreast of updates.
You are welcome to ask for new features. I have my own ideas, but would love to hear from you.

P.S. If you find MaGog useful, please also consider registering in The Directory of Public Wishlists thread. Read about it in post #1 of that thread.

P.P.S. MaGog is currently in Legacy Mode. In this mode, she ignores games added to GOG in the last year or so (a sliding window, updated once a month), while fully monitoring games added to GOG before that. The reason for this is GOG's decision to add games with in-game purchasing (i.e. Gwent) to its catalogue. If and when GOG removes Gwent, or does something equally monumental (e.g. begin selling DRM games, or single-player games with in-game purchasing), MaGog will return to her full-blown regular mode.

This is fantastic! And yes, you're not alone, I too have found the search system in place to be lacking a lot of crucial features. I'm using Chrome (v 35.0.1916.114 m) and seems to work fine so far. I'll let you know if I find any issues in the future.

Thank you! +1

Some examples of (more or less) interesting searches you could do:
1) Games with at least 4.5 stars and 1000 user ratings, sorted by descending order of number of stars and number of user ratings
[url=http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmbaxyv&ord=s9n9&flt=sat~4.5~nat~1000~]http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmba&ord=s9n9&flt=sat~4.5~nat~1000~[/url]
2) Games removed from GOG, sorted alphabetically
http://www.an-ovel.com/cgi-bin/magog.cgi?scp=r&dsp=ipgfsorlcmba&ord=&flt=
3) Games with no bonuses at all, sorted by release date
[url=http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmbaxyv&ord=r0&flt=bnb~1~]http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmba&ord=r0&flt=bnb~1~[/url]
4) Games that offer both Finnish and Hungarian support
[url=http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmbaxyv&ord=&flt=lal~FinHun~]http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmba&ord=&flt=lal~FinHun~[/url]
5) Games that officially support Windows 8, but not Windows 7
[url=http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmbaxyv&ord=&flt=oan~w08~onn~w07~]http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmba&ord=&flt=oan~w08~onn~w07~[/url]
6) Games currently on sale
[url=http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmbaxyv&ord=&flt=pos~1~]http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmba&ord=&flt=pos~1~[/url]
7) Turn-based RPGs of the 1990’s
http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmba&ord=&flt=gal~rpgtur~rne~01011990~rnl~31121999~
8) Games costing up to $15, no larger than 1.2GB, supporting Vista but not Mac, published in a month with “r”, not supporting either Brazilian-Portuguese or Bulgarian, having multi-player mode, having avatars and a manual, and not containing “Settlers” in the title
[url=http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmbaxyv&ord=&flt=pnm~15~fnm~1.2G~oan~wvi~omc~0~rma~JanFebMarAprSepOctNovDec~lnn~BraBul~man~m~bal~avmn~tds~settlers~]http://www.an-ovel.com/cgi-bin/magog.cgi?scp=gdr&dsp=ipgfsorlcmba&ord=&flt=pnm~15~fnm~1.2G~oan~wvi~omc~0~rma~JanFebMarAprSepOctNovDec~lnn~BraBul~man~m~bal~avmn~tds~settlers~[/url]

The options are as limitless as they are silly.

Note: The links above are sample outputs of the search engine. You can “save” searches you would like to repeat by simply bookmarking the results page or copying its address (i.e. all the information is in the URL).

This is quite the remarkable effort, well done!

Personally, I've been trying to figure out what is and isn't Win8 compatible, so this fixed me up right well. Also, results weren't as bad as I feared :-)

Wow, I'm very impressed. This is fantastic work mrkgnao! Well done :-)

GOG, I hope you are watching this thread.

Wow, thanks for the effort mrkgnao!
I just tried it - it works great. This will come in real handy.

+rep, this is much needed.

GOG should implement this.
Great job!

Nice work:)

This is an awesome piece of work, please get it sitckied.

I would hug you mrkgnao (in a manly way) but I wouldn't want to give the wrong impression, so please accept a manly rep boost instead :)

Great work :)

Fantastic job, huge thanks! :-)

768 games support windows 7, 711 support windows 8.
It's actually way better than I thought for windows 8 users.

Good work.

Fantastic! +1
Now if we had a good search engine for the forums....