I'm not so much of a Codexian that I want to shame people for listing Oblivion and Skyrim, but the amount of people listing them without including either Daggerfall or Morrowind is rather eyebrow raising.
Or maybe I'm just old.
Daggerfall and Morrowind are overrated and there really wasn't much reason to play them a lot. Old does not mean better, despite what the morons on this forum claim. Daggerfall was a weak game mostly memorable for being huge random generated world with no depth and tons of bugs, and Morrowind is mostly remembered for the giant mushrooms and for being like the only decent 3D first person game you could play using swords and bows and magic instead of rifles. People tend to overrate these games a LOT simply out of nostalgia.
Skyrim on the other hand was a fucking masterpiece. It is also leaps and bounds above its competition, even 9 full years after release. I mean, honestly, if you want to play an open world first person fantasy CRPG, what are your options today, 9 years after release? Yup.....
So it makes sense that people play it a lot, especially using mods to keep it fresh.