Online gaming started w/ Shadows of Yserbius on Sierra's ImagiNation Network, AD&D/NwN on AoL - but was 11-13 and wasn't too great.
Competitive gaming started w/ WC2 through keyword battlenet, on AoL in 1995 and stopped after the decline of competitive gaming on the PC, and quality games for the PC format in general shortly after WoW set a new standard of forced 'there are no losers as long as you give it your best' mentality.