At first i thought i was becoming horribly addicted to Civ World. However after completing 1 or 2 full games i found my interest waning...
Civ Rev (my favourite game of all time) has scenarios or MP and teams and Game of the Week...all make it incredibly re-playable...cos of different maps, different artefacts, different people. I'm still playing it 2+ yrs after it was first released.
Aside: I am playing Civ World at work now...cos i'm battling various bureaucrats and red tape...it's reverse psychology of sorts...my 'net usage will flag management and they'll be compelled to give me some work LOL
(So 2K, can you please make each game different somehow?!!)