Syberia was good... Syberia II is also good, but no improvement
Just about everything I liked about the original Syberia, technically. It's the same interface (some people might dislike this, as there's no improvement on either the interface or the graphics, but Syberia I was so outstanding there really was no need). Also, this game starts right where Syberia I ends (it ended in a cliffhanger, of course), so the sense of closure is nice.
The storyline took a step back from the moody, melancholy first part and attempted (not entirely successfully) to add humor to the game. Unfortunately, as much as I like humorous adventure games (Monkey Island, etc.), this is NOT what made Syberia great and it seems out of place. Hans Voralberg was a great mystical character in part 1, and over here he's a drooling retard. The two recurring villains look like they jumped right out of 101 Dalmatians or something. Could have done without it.
The Bottom Line
Buy Syberia I. No question about it. You'd want to play the game in the chronologically correct order anyways. If you like Syberia I, then go get Syberia II, because it's essentially the same game and continues the storyline, so you'll like it also. But as a standalone game it's nowhere near as good - if you play part II while never having played part I I doubt you'd enjoy it half as much.
Either way, a welcome addition to any adventure gamers' library, for sure.