These are a few games I've played mostly because of GOG sales.
Gemini Rue: I liked this one a lot. The plot twist was pretty well constructed. The puzzles were pretty easy but there were some really greatly designed ones. It gets an A.
The Witcher: I got it free from a GOG promo. Basically I can't get myself to like this game. It kind of seems like they put the worst elements of Fable and Neverwinter Nights together to make a rather bland experience. Also, I'm cool with the idea of being able to have sex in an open world game, but the way they present it (ridiculous cutscenes with hardcore porno sounds and then receiving a trading card for each lady) was pretty gross and made me feel kind of put off. I also just really don't care about Geralt at all.
The Cat Lady: This is a pretty fucking great game. Sure, it has its plot holes and at times it plays more like an interactive cutscene than a game, but the art direction is great, I genuinely liked the main characters, and the themes are pretty heavy and thought provoking. I recommend it.
Wasteland: I haven't gotten too far in this yet, but I'm still on the fence as to whether or not I want to keep playing it. I'm a huge Fallout freak and I play through at least one of them annually, but while I can see this game's influence it really hasn't aged well. The mechanics are pretty ahead of its time, but the execution is kind of shitty. Also, the scenario design is just kind of weird (Find hidden cave, kill rabid dog, get attacked by savage children which causes the river to dry up and The Red Ryder to come and attack you for some reason.) I'll mess around with it a little more, but I probably won't play through it all the way.