HunchBluntley: Yeah, the GOG-published ones include 6 bundles comprising 20 games, plus 2 more sold individually
eiii: I haven't played any of these old games which are now owned by GOG. All of them are high rated, but a part of that rating probably is for nostalgic reasons. How good and playable are these games still today?
I guess it's also a matter of taste and interest, but personally, I think, with the exception of
Forgotten Realms Unlimited Adventures (FRUA for short), the
Gold Box games aren't all that attractive for new players today, due to the really basic 80's EGA graphics in some of the older titles (no real pixel art, just rather crude stuff, IMO), their use of journal entries (instead of describing in-game what's happening, they often refer you to read passages in the manual, which is even more annoying nowadays when you only get a digital pdf copy of it), GUI (e.g. press M to move in combat, instead of just move), and a lot of combat vs. rather simple stories. That's my personal view and bias, in any case, as someone who didn't play these games back in the days. If someone is a massive D&D geek, has a vivid imagination, loves hacking and slashing and doesn't mind the issues mentioned above, they might still be able to get into them. I couldn't.
I'm a big fan of FRUA though, the Gold Box construction kit which uses the most advanced engine of the Gold Box games with slightly better UI, VGA graphics that aren't as bad anymore, and which also allows for inserting your own pictures. The best thing about it is that there is a small but still active and very nice community for it that has expanded the editor's potential via hacking and modding, and that there are scores of free high quality
fan made adventures available for it on the net. And you can easily create your own ones as well, if that's something that interest you. The only downside is that you have to jump through some
hoops to set up the GOG version in a way that allows you to experience all the hacked content, but it should just be a matter of 15 minutes or so, including the reading, and after that you're up for hundreds of hours of fun. So IMO, the FR Collection 2 is totally worth it, even for new players, but mostly for FRUA - and provided you're into D&D, turn based combat and reading.
The 3D dungeon crawlers from the Eye of the Beholder series and Dungeon Hack still look and play great today, they are perfectly accessible for new players, though with the caveats that (a) the Eye of the Beholder games don't feature an automap, so you have to either map out the dungeons yourself, get the maps from the internet or just find your way around the dungeons without a map, which can be tricky in some spots regarding teleporters and secret doors, and that (b) Dungeon Hack is just a randomized dungeon crawl without any story-telling aspects to speak of, so depending of what you're looking for, you might become bored with it after a while.
I'm not quite sure about the rest of the games. I loved Al-Qadim back in the days, and it should still be accessible, but I couldn't bring myself to replay it now. The Ravenloft. Menzoberranzan and Dark Sun games always interested me, but I never played through them and I think I remember they were plagued by some more serious bugs, but I might be mistaken.