Skyrim for 203 hours.
The most time I've ever put into a series of games though is probably the GTA series, because once it came to mobile phones, I'd play it all the time just driving around and doing fun stuff.
I've probably spent around 6000 hours altogether on Minecraft, by far and away the game I've played the most:
World1 143.18 days 3436.32 hours 985 sessions
TMCWv4 22.46 days 539.04 hours 140 sessions
TMCWv3 15.83 days 379.92 hours 104 sessions
TheMasterCaversWorld 14.72 days 353.28 hours 103 sessions
World1v2 8.57 days 205.58 hours 73 sessions
TripleHeightTerrain 8.25 days 198.00 hours 53 sessions
World1v3 7.27 days 181.68 hours 59 sessions
TMCWv2 5.62 days 134.88 hours 52 sessions
InfiniteCaves (recreation) 4.17 days 100.08 hours 29 sessions
Total 230.07 days 5521.68 hours 1598 sessions (3.46 hours per session)
All of these times are from the in-game stats so they are the exact times I spent in each world. This also does not include several early worlds I had (including the original "InfiniteCaves" world, which I'm currently playing on as a recreation, this was the first world I had with modded cave generation), the time I spent on a modded copy of World1 (IIRC, somewhere around 10-15 days), or all the time I've spent on developing mods, which has significantly exceeded my "real" playtime this year (I count this as playing the game still, I even have over a day of time in several test worlds, including doing actual gameplay in them to verify that everything is working).