Since City of * starting having some lag issues with their packet carriers in Europe somewhere, I went back to playing some OpenTTD. This game has such massive replay value it’s hard not to just install it when bored. I have started using the replacement GRF files too in order to change the game and give it another new lease of life. You can find a list of GRF files on the OpenTTD wiki, over here, http://wiki.openttd.org/index.php/GRF_List
The other decent title out at the moment, similar in play style to Fable by Lionhead Studios, is Overlord. This is a superb game where you play an evil Overlord with a horde of minions with which you wreak havoc among the populace. Fire, brimstone, even your own evil tower! Great game.