For people who don't know these games, here's a quick, at-a-glance comparison.
The biggest difference lies probably in the scope of the games. You have an immensely vast, diverse world and (almost) total freedom in Sacred vs a much more concentrated, quite linear story in Divine Divinity, with both having its strong and weak points.
-Sacred's huge, open world means that you can pretty much go wherever you like (between certain limits, enemies are even scaled to you, so that's not a problem either) and although there's a main plot, you don't really need to concern yourself with it (only to reach ever higher difficulty levels). However, it also means that the world isn't very detailed (however, it's certainly not generic), and while there are about a gazillion side quests, the NPCs are anything but remarkable and even the rewards aren't that good.
In essence, it's all about looting, grinding and gaining levels.
-Divine Divinity, on the other hand, is much more detailed, with much more likeable (or despicable) NPCs, a more interesting plot and quite a number of unique locations. However, the world is much smaller, so you'll quickly get to know everything, enemies don't respawn, so there's no infinite XP/loot and you're mostly forced to follow a set route or face insta-death from creatures waaaay over your level.
Which you'll like more can thus depend on whether you want a loot-and-grind fest or a detailed story and world. Both are backed by awesome gameplay mechanics.
Post edited June 24, 2012 by DrIstvaan