I liked Medieval II because in the newer ones I have been terrible at musket fire and cannons and I only really enjoyed the Naval battles. I remember I played as Russia on Normal once and took over the majority of the Ottomans and all of India and hardly use my Ranged Units as directed. Extremely hard but fun. I always have good strategies in Melee.
I think I liked Empire the most. Maybe it's just the time period, but I think it's really awesome. Napoleon comes in a close second because it is basically the same game, with better gameplay, but comes with a significantly reduced campaign experience.
For its time, nothing beats Rome. That game was so awesome. Heaps of new features and innovations, epic setting and scope, very polished, endless content. Then Napoleon (especially with mods), and I'm also really enjoying FOTS. Get DarthMod for Napoleon if you still play it. Improves the game a lot in many different areas, especially the campaign.
Medieval 2 is my favorite, but Rome is a close 2nd I haven't played empire enough to develop an opinion yet, however I am not a fan of the period.
I voted for nappy, because I like the.....guns-I like the guns and the lines. And I feel like it's more polished than empire.
Voted for Rome. It's the only one I keep coming back to over the years, and it's got one of the biggest modding scenes in gaming. Being able to download what essentially amount to whole expansion packs for just about any time period you please, most of which are developed to an almost professional quality is pretty awesome. It also has probably the most flexible and robust engine out of the lot.
I really like both Rome and Empire but I can only vote for one so I say Rome because Romans are cool.
Empire total war is my favorite, having such a huge map and vast range of factions to play as was great. Lot's of replay value! Second favorite would have to be medieval 2, love the time period! (knights, swordsmen, etc)Also with the kingdoms expansion that added to the experience.