Humans are inherently social creatures. Therefore we have evolved our gaming to the most social it can be, massive multi-player on-line games.  Today's MMO genre of gaming grew it's roots from text based Multi-User Dungeons (MUDs), like Tempered Steel, commonly played over a telnet application by thousands of players simultaneously. MMOs were popularized with the rise of Ultima Online and Everquest in the late 1990's, and today, some of the top played MMOs boast 12 million subscriber accounts.