According to Steam:
- Rocket League: 2038 hours
- GTA V: 260 hours
- Project Cars 2: 234 hours
I haven’t seriously played any of them over the last year though. RL has been run into the ground by greed. GTA V was always greedy, but was still some fun to fck around in. However it isn’t really relevant anymore. PC2 was replaced for me by Assetto Corsa (5th place, 170 hours) which has great mods and better physics.
Also, this is only Steam. Combining Steam and Uplay numbers, Trackmania 2020 probably 2nd place with just over 300 hours. And LoL may also be top 3 even though I haven’t played in years. Likewise Beyond All Reason may be getting close to the top 3, but I have no way of knowing since it doesn’t track the playtime afaik.
They also say “and reinterpret in base 10”. I.e. interpret the base 2 number as a base 10 number (which could theoretically contain 2,3,4,etc). So 10 in that number represents decimal 10 and not binary 10