Almost every MMORPG. They start off fun and then the fun becomes grind - tedious quests, upkeep, travel time, hp recovery, crafting, rare spawns, penalties & debuffs for death.
My first experience of all this was Everquest. I quit because Verant screwed up a series of expansion launches leading to crashes and downtime and I questioned why I was playing this thing and realised it hadn't been fun for a long time. But pretty much every MMO is the same.