I'm over 10k hours on FFXIV, been playing since launch. Could get an exact answer when i get home. Next closest is Skyrim with around 1,500.

Edit: it's over 14k hours, more than 584 days worth. It'd be much more if I had more time the last two years but I can't do much than dailies with a 15 month old!

I'm over 10k hours on FFXIV now... but on the plus side it's where I met my wife and some good friends, so the hours I put in paid off.