I suppose you would find my way of winning cheap, but it works. Start of by going straight for Map Making. Once you get there, immediately build the great lighthouse. Then, find out where he is, and box him in (if on the same island, build cities around him, if not then build a fleet of galleys and block him so his galleys can't go to other islands. Then, having free range on the ocean, never stop producing settlers in your capital, and proceed to take over and colonize the rest of the world. The last game I played, I ate his 12 cities with cavalry, while he defended with pikemen.