Diablo 2

[Lucifer]

No, you don't. You can transfer your characters from Diablo2 to Expansion anytime. However you can't transfer them from expansion to normal again. And yeah act2 is a bitch.

[Lingus]

Well, considering the storyline will pick up many years after Diablo2 I'm not sure exactly how much will be taken from it's storyline. Certainly something of the main story arc of Diablo2 will be used. But w/e. If you don't care about the story it doesn't matter. I just think Act 5 and the conclusion that LOD offers is pretty cool. So you should do it.

[JoEL]

arghhh peer pressure! Ok I'll buy it soon...it's still pretty expensive for an old game.

[EpicPhailure]

The only confirmed tie-in is that there's the three Prime Evils (Mephisto, Baal, Diablo), and that the Barbarian class is the same barbarian you play in Diablo II.

[Lingus]

Well, it is supposed to take place in the same fictional world. All of the history of Diablo 2 and Diablo 1 is all the same for Diablo 3. Everything you learn about in those 2 games and in the expansion will also be true for Diablo 3. There will also be something like 30 years or w/e between the end of Diablo 2 and the next game, but the point is there is more tie in than those few details. There's stuff that you won't have the history on if you don't play the other games... Given, there's not too much plot and back story, but there's enough.