#1 C3 Hardest to build a stable city, western preference for Rome, sentimental fav because I started with C2.
#2 Pharaoh/Cleo a bit easier than C3 but add monuments.
#3 Emperor stable city harder than Zeus but much easier than C3 & Pharaoh. Love the graphics and art, still learning the fundementals.
#4 Zeus/Posiden still fun. But I only play it for contests.
I also play AoE2 but only when I have just an hour to play, or to be destructive when I'm in the mood, a break from city building for a day or 2.