I found the Venetians the easiest. Buying Bologna on the first turn, taking Florence and crushing Milan as well as getting everyone to pay you for alliance is great. I also managed to land my force on Crete next to Corinth on the first turn and siege it on the second. The Byz were crushed in short order. I also quickly took Antioch through a crusade. By turn 20, I had most of the richest lands of the game all in my hands.

Most fun is probably my Russian game right now when I decided to relocate to Britain. I think that any relocation game might be fun. Turks are also a blast. I'm a big fan of horse archer armies.