As always, it depends.
Games that are very linear, and that focus heavily on a narrative, generally work best if they're not too long, as it's incredibly hard to sustain interest for dozens of hours - and it takes quite a storyteller to maintain momentum throughout such an experience.
That said, I'm not sure there ever was a truly huge game of that sort.
Arguably, I think Deus Ex: HR was very big considering the narrative strength and the linear layout of missions. Of course, each individual level was open and relatively non-linear - which helped a lot. But it might be one of the longest games of this kind.
Same is true for Vampire Bloodlines, which while having some degree of non-linearity - really is a game driven by a main narrative. It's also very, very big considering the density of the story material.
But, if I think of something like Shadowrun - I don't think it would be able to keep me interested for much longer than it does. It doesn't have enough meat on its system bones. It wouldn't really matter if the story kept being "interesting" - as I would be bored to tears of the simplistic mechanics.
Skyrim, on the other hand, has a very different structure - and it essentially allows the player to finish the main story relatively quickly, and the rest is optional. That's a great way to go about it - just as long as the sidequests are interesting. Otherwise, it might as well be a bit longer and have more resources dedicated to the main narrative. Personally, I think Skyrim should reduce the ~3-400 locations to ~50-100 locations and give them that much more attention, but that's another discussion.
But I voted 60+ hours - because I absolutely adore huge RPGs. But I think there should be room for all kinds. All shapes and sizes