Probably first graphic Internet game was designed and released by LucasArts in 1988 game, “Club Caribe” on Commodore 64. Well, game wasn’t classical RPG but players could coopered with each other. First MMORPG game was Neverwinter Nights, developed by Don Daglow and Cathrine Matag.
For real MMORPG games we had to wait till game Meridian 59, developed by 3DO company in 1996 (yeah these guys also created “Heroes of the Might and Magic” and all “Might and Magic saga”!).

Another interesting project was titled The Realm Online created by Sierra Online, few months after Meridian 59. Game has animated 2D graphics and real 2D combat, it was really huge phenomena back then. Later Ultima Online, released in 1997, may be credited with first popularizing the genre.
Probably first and most successful MMORPG was EverQuest released in 1998 and later Blizzard’s World of Warcraft dominating as the largest pay-to-play MMORPG.
Well, now we’ve got many free or pay for play MMORPG games, but WoW is still one of the most popular games in genre.
Maple Story or RuneScape are also very popular and are free to play for everyone. Maple Story has around 50 millions players worldwide! It’s absolute record. Market is growing really fast and who knows how future will look like…