Hi, LEXX.
I never played Sacred II, so I'm not qualified to talk about it, and I will tell you what I think about Sacred I.
The game take about 40 hours, so it isn't so long. The map is huge, but exploration it's not good because you can look around, but because there are:
10 dragons, almost impossible to find;
A lot of easter eggs like Tristram, the Pacman Cave, the Pong cave, the Friday 13th items and a lot of others;
Side quests.
Side quests help you to raise your character a lot, as they give you money, experience, set items and runes!
Anyway, I don't think I can change your mind, but I hope you will like the games.