Get them both, if you can.

I've heard good things about both, but I am really tempted to buy Syberia since I can get it for a buck at my local second-hand store. I'd go with Syberia, since there is two games and more story.

Think about it this way. If you would have bought one out of the promo it would cost the same as getting them both now.

I've only played Syberia (And I havent even beaten it yet), but I can tell you that it is very enjoyable. The story so far is quite good, but it's really the scenery that makes Syberia top notch. It feels very Myst-like, which is something I find very nice since Myst is my favorite game of all time. However I've never heard anything but praise for TLJ, so it's probably just as good a choice as Syberia.

I haven't played The Longest Journey Yet. I have it though. :D

But Syberia is truly a great story, and it kind of has the look of a used universe, like Star Wars. This story, and the atmosphere of the game itself, for me, is like sitting in a comfy chair on a rainy Sunday and getting buried in a good book.

I'm really hoping The Longest Journey gives me just as enjoyable an experience.

They both fall into your requirements. May I suggest that you pick up The Longest Journey while it is on sale. By the time you finish it they may have a Syberia Sale where you could get them both and save money too. Good Luck.

Pleanescape Torment! Oh wait, sorry. Out of those 2 games, I would lean towards syberia a little more but its a bloody close thing since they're both creative adventures with interesting characters and good atmosphere