If you've got no problem wkith steam, I definitely recommend The Dig, one of the best adventure games I've ever played and definitely the best non-comedy one

Nobody mentioned Sanitarium? That game is utterly fantastic... so creepy and atmospheric.

My favourite adventure games:
Monkey Island 1 - 3
Broken Sword 1 & 2
Sanitarium
Grim Fandango

You can't go wrong with games like Full Throttle, the Discworld series, Sam & Max Hit the Road, and Day of the Tentacle either. All solid games.

On GOG, The Longest Journey is pretty good, but I didn't find it to be as good as most of the ones I mentioned above. It's got an interesting story for sure, but something about it just didn't really click with me. Same with Syberia (I'd rank Syberia lowest of all the games I mentioned, actually), with its very simplistic puzzles/gameplay, it's more like a interactive storybook than a full-fledged adventure game. Then again, you might like that, so whatever...

All EXCELLENT choices, and the ones I was going to recommend.

Chaser is 'all right'.
For $2.99, you cant go wrong, right?
Maybe leave it until you play all the great games though.

Unreal Gold is good.
Psychonaughts is good.
Duke Nukem Manhatten Project is a great side scroller.
Judge Dread was a surprisingly good game. I didnt have much expectations for it, but it surprised me by being good (not great, just good though, or maybe somewhere in between good and great lol).

Raptor call of the shadows is a top down flying gunner game. Kind of mindless, and not my favorite game, but probably worth having on sale if you like top down scrollers.

Anyone notice both Lure of the Temptress and Beneath a Steel Sky are both free?.

If text-based was all you ever played & you never got into later adventure games, then the King's Quest 1+2+3 & Space Quest 1+2+3 bundles could be for you. Same basic text commands, but with EGA/VGA graphics, great storytelling, and some humor (more in SQ than KQ). Remember, these were the original graphic-adventure games that started it all!

P.S. Sorry for getting to this "party" a week late. :-)
Yes. They are 2 of the 4 "always free" games from GOG. Pretty generous of GOG, huh?

FUCK the Quest series. The puzzles are too random and "pulled out of you ass" for me, some are nigh impossible to work out without a walkthrough manual. Oh and the insta-deaths are sheer BS.

Thank you, come again...

You gotta play The Longest Journey. It is simply outstanding game.

Sanitarium was fun and not really too hard. Messed up at times tough.