World of Warcraft at launch.
You want your solo rpg? That's fine you can basically mess around by yourself if you want.
You want multiplayer? Also fine, plenty of content for multiplayer.
Lots of secrets, a massive world, tons of content, the perfect fantasy RPG. You can become guild leader or raid leader as well and learn some people/ life skills. The game was challenging when everything wasn't so freely available to everyone. All the classes are fun. PVE and PVP are vastly different skills.
I quit during Warlords of Draenor, and came back to WoW classic and quit again. Came back for Wotlk classic and Season of Discovery last year and quit again. The game is still fun and still completely worth playing. But my decision to save time and experience more of life is also valid. Basically searching for that game that can surpass it.