[Newworlds]

I know what you are talking about and there isn't really a Text based game like that that is active, however, if you aren't only into hack and slash and want some powerful roleplay along with hundreds of active players you might try New Worlds Ateraan.

In this world you can join the Northern Kingdom or the Southern City State and between the racial, religious, and political conflict you will find a similar style of play or at least the closest thing to large powerbased conflict that you may find anywhere. You can, in fact, build ships, clans, houses, and castles, and forming alliances politically and socially is the key to success.

BUT.

It is not a city vs. city game in the sense of Empire. However, we just had a week and a half of a global roleplay event that over a hundred players have participated in. Gotta love that!