I'd have to say that Empire is my favourite. Napoleon has many great things to be said about it. Give me Napoleon with Empire's map and we can call that an easy victory. But what they're doing with Rome 2 is blowing my mind.
dirtyharry50: How is Rome? I'll be new to the series and plan to start there. I own it already.
It's very good in a lot of ways. The only problem is that it discourages expansionism via means of an absolutely insane 'distance to capital' factor that turns any territory too far from your capital into the most rabid, murderous bunch of anarchists the world has ever, or will ever see. But it's not a bad one to start will so long as you keep in mind that your focus is on conquering all of Rome.
Medieval 2 isn't so... restrained and takes the leash off. Which is why I prefer it.