Oblivion is not multiplayer sadly.
I have been enjoying Civilization 4, both single player and multiplayer with friends. Is a very solid (My opinion) strategy game, and can easily suck you in. In the multi player you can be on same team or not, and if life gets crazy around you can can hit save and come back to the game at a later time (in multiplayer). Something about starting a cizilization in the stone ages and taking over the world realy appeals to me I guess