Slightly different type of game, but a strong mention for Runescape, specifically old school runescape as it takes longer to max.
A mod tweeted the record for fastest "Maxing" (highest level in each skill) to be ~2136 hours. This is just for one game mode where you can trade other players. For a gamemode "ironman" where you are on your own and cannot trade, the record is ~3400 hours.
This is also just for what we call maxing which is 99 in every skill. You can take this further by getting 200million xp in all skills which is the max amount of xp in a skill. A handful of players have done this now, which is estimated to take about ~15,000 hours.
Source
This equates to:
To put this into hours:
Normal: 2156
Ironman: 3522
Ultimate ironman: 4954
Hardcore ironman: 2863
Key points:
- Normal is the fastest because you can trade and buy supplies to level up with
- In Ironman game modes you play solo, you have to collect everything yourself and you cannot trade other players
- Ultimate ironman is the longest because you have no bank, you have 28 spots in your "bag" and have to use it wisely
- Hardcore ironman means you have 1 life, when you die you return to a normal ironman. Maxing this game mode tends to be faster than maxing a normal ironman because you tend to do less dangerous things such as bossing when you have one life, so you spend more time training and leveling up skills