If we’re just talking video and computer games…probably Zelda: the Wind Waker. At one point, I decided I really wanted to get all the figurines. That takes a while.
Life.
I played the original Fallout for at least a week without breaks for anything other than food and sleep.
Yeah, but how many of those days were spent sitting in safe spots waiting for local to clear? 
The very first Mario seemed like it took forever. The original Pool of Radiance was a long one too.
Yeah, but were they actually doing anything in the game for all those days or just having their characters learn skills?
I think the game I’ve spent the single largest amount of time on (besides the MMORPG Anarchy Online) has to be Diablo 2. I spent something like 4 years playing this, more than a few times for over 16 hours straight.
But I’m feeling much better now 
They don’t have to be logged in for their characters to learn skills, that happens automatically. But admittedly they did leave it on in the background while tending to their duties.
same save game eh? Wizardry. it took me quite a while to complete Wizardry 7, after which i kept the same save game for 9 years to continue playing in Wizardry 8. technically i’d wasted no time and was playing at the publisher’s pace.
what do i win?
Nothing, as you’re not competing in the same event 
What I meant is; how many playing hours have you logged on the same save game.
Back in the day, when you only had a single save game file, I think either Bard’s Tale or Pool of Radiance on the Commodore 64 for me. I know I put in over a hundred hours on each of those games.
Because you could port your save game file to the sequels, technically Bards Tale 2 & 3 were each probably an additional 100 hours.
Most PS/PS2 native CRPGs I’ve logged at least 200 hours on single playthroughs (usually my second or third) - FFXII being the one exception I can think of (remakes, like Chrono Trigger or Final Fantasy Origins don’t count) - I stopped and just went to the endgame after about 120 and 150 (first and second playthrough) because I was so annoyed with the sidequests - Yazmat, and Zodiark, specifically. Though Yazmat accounts for 20+ hours in each play.
For boardgames, I’ve had Risk games go for 12 or more.
My Pokemon Ruby game has topped 100, I’m looking forward to pushing Diamond into that range, when I finish the main plot and start playing as a Coordinator.
You win nothing unless your Wizardry 8 party started in Wizardry 6. Mine did.
In fairness, a completed Wizardry 7 game takes hundreds of hours. That save can be imported into Wizardry 8, which takes less but is by no means a quick play. Does it count as the same save if it’s imported across games?
Sure, I’ll count that.
Probably Final Fantasy XII - I think I topped off at about 90 hours. The big one, though, is Ultima III for the NES. Games didn’t track playtime back then, but I can only imagine that it was at least 150 hours, possibly more. Unbelievable how much time I spent on that game as a kid.
I spent a year playing Super Mario Brothers on the SNES. Obviously, I’m not a hard-core gamer, although my playing-through times have gotten much better.
I still get a pretty good dollar/hour value out of games though.
The Archibald campaign in Heroes of Might and Magic 2, the first time around. I was a kid, still poorly attuned to the notion of rushing. I think I spent a good fifteen hours chain-failing the “Country Lords” chapter before I gave up and went back to the first fork in the campaign for the bonus ogres. It took even longer to beat it afterward. The rest of the campaign wasn’t too bad, though.
Curse of the Azure Bonds - My party got to about 13th level and I just stopped playing, it took me maybe 20 hours of play to do it cause I kept dying in the sewers in Tilverton.
I really can’t recall how much time it took, but beating GTA III and Vice City took awhile.