re: Crusader Kings 2 is insanely addicting

Well, Iberia and France were kind of easy mode by the 1300's if you don't have Aztec Invasion. The East is dealing with the Turks, Timurs, and Mongols and all you have to worry about are the HRE and North Africa.

Plus, it can be interesting to bring superpowered Aztecs and Incans into EU4.

But yeah, Sunset Invasion is by far the worst expansion...or maybe least useful expansion.

I'd rank them (in terms of new interesting content):
The Old Gods-new start date in 867 allows you to play as pagans. Can do Viking raids
Legacy of Rome - allows you to build a standing army and adds a ton of new events
Charlemagne-769 start date, new events, custom kingdoms and empires.
The Republic - let's you play as republics and adds mercenaries for hire.
Horse Lords - Allows you to play as nomadic hordes. Pretty fun actually. I just like playing republics more.
Sword of Islam - lets you play as muslim rulers
Sons of Abraham - adds Judaism to the game, adds more Holy Orders. Makes heresies more powerful.
Way of Life - seemed interesting at first, but doesn't really add too too much. Lets you set a focus and gain new events and stats...but meh
Rajas of India - lets you play as Indian rulers
Sunset Invasion - makes superpowered Aztecs attack Iberia, France, or Ireland.