But the three games are all so different????

It really comes down to your preference, on another fourm one guy was ranting about you know the SF thing and someone suggested another game that was great and didn't have SF. My answer was while I had no problems even if I did I would not play something on a subject of no interest to me because of SF. I know civvie FS simmers who would not touch CFS cause they hate combat and combat sim pilots who think civvie FS is boring.
Anyway, MSFS 2004 is great and has a huge world of addons, can't really go wrong. CFS3 meh, except this new addon already mentioned for WWI which I have heard raves about. Age of Empires never played it but loved Civilisation back in the day so if it is like that should be good.