The latest add-on, Anno 1404: Venice would be out. It is one of the best Sim City fused with RTS and RPG goodness out there in the market. Played with it for days on end and it doesn't get boring. The latest add-on will allow 8 players to play successively. So just imagine Sim City but you are playing with 8 people, with resource chain management and naval battles. I don't know how the hell they will implement it but their taunted features looks cool.