My only completed long campaign so far has been Venice, and that was fun enough until the late game where my borders were so massive that I got declared war upon by every faction touching them. Then it turned into a bit of a slugfest.

So far, I'm only at around 1140 or so in my Spanish short campaign and I have to say it's really good fun. I don't know if it's the fact that I know much more about the mechanics of the game and thus alot of the "playing in the dark" feeling has gone, but the peninsular war between the Moors, Portugal and Spain is alot of fun. I even had France come knocking in the middle of it, arriving with a full stack at my northern borders. While all I head was a small, dusty (but damn experienced) Iberian army of Jinetes and Alumghavers skirmishing with the Moors in the mountains to the south. Really captured the spirit of La Reconquista, I think.