I'm currently on "vacation." "Vacation" in the sense that I'm stuck in a boring town with nothing to do but play games.
I go through phases of playing New Vegas and not playing it. Y'know, cause it's a great game, but I've also played 930 hours of this great game so nothing is new, so every so often I need a hiatus from it, then when I come back things feel fresh-ish again and it's fun all over?
Well yeah, I started this "vacation" while on a hiatus from New Vegas, and it's kinda depressing how hard it is to play FO3 or Skyrim. When I get back into New Vegas, I'll sometimes spend an entire Sunday just playing the game, but here? I turn FO3 or Skyrim on for an hour or two, it gets dull and I decide to "take a break and go watch the news/random crap on youtube" and then I never end up going back because the games simply don't grab me.
I think a VERY clear difference between the two is that New Vegas has plenty to discover. "But Longknife, Skyrim r pro at exploration, New Vegas r teh svck1!1" I don't mean world exploration, I mean character-wise. I can start up New Vegas over and over, try a COMPLETELY different character build and stumble upon a build that finally makes a unique weapon I've NEVER used before a god-tier weapon. This gives me incentive to keep playing. This makes me want to keep going, to see what happens when my character unlocks that new perk or finishes that quest chain to see that new item. For example if I have a character that's great with Lucky, then I can't wait to get my next perk and take Finesse. Or if I have a character that's superb in VATS, I can't wait to see how well the different unique guns do in VATS now and I go around collecting them all. It's like an experiment every time, and there's always something new to discover.
Skyrim has world exploration yes, but why the HELL should I care what's in random cave #437? And what happens once I've seen cave #437? It's boring forever now, because I know what's in it. That sense of discovery is gone, and that sense of discovery dies quickly since the method of discovery -LITERALLY- just involves walking into every cave you see, whereas New Vegas requires some insight, research and/or creativity to discover a new character build that kicks ass. You may think the Sprtel-Wood 9700 svcks, until you realize how Laser Commander, Light Touch, and ED-E's Lonesome road perks work. Then suddenly you have a theory it'd be good and you can't wait to test it and see the results.
In that sense, I think that New Vegas has far more discovery to be had, and it's far more gripping than Skyrim. In New Vegas, I start a character with a theory of how to make him strong and I can't wait to prove it. In Skyrim, why would I say "omg I can't wait to see cave #437" if I'm not even yet aware that cave #437 exists, and when there's 436 other caves that were "meh?"