World of Warcraft
Final Fantasy XIV
WoW is the biggest MMORPG there is and it laid the foundation for a majority of the MMORPGs around today. It has a long deep history in terms of lore and gameplay and has sparked countless other games such as Hearthstone, Heroes Of The Storm etc. WoW will always remain as the MMO juggernaut for quite some time.
Not only is it still thriving, unlike WoW, it has more players than WoW ever has, you can be all the classes with one character, it has a better support staff than WoW does and its SquareEnix (which is better than Blizzard)