Sorry, but New Vegas was a travesty of world building. While quite good from a character-building perspective, the world was Ugly, small and static. While Skyrim may railroad character choice, New Vegas railroads exploration, and if you can't see that, you're blind.
again, I got out of the start town and wandered through most of the map randomly doing side quests and entered Freeside without problem. care to cite specific examples of railroading?
as for the world, it wasn't the most detailed, yes. but it was actually more varied in it's tile set than FO3. in NV you had: generic badlands, Red Canyon area, NCR Camps, Some green areas, New Vegas area and the strip.
In FO3 you had... Generic completely uninhabited badlands and the inner city ruins. that's it.
You shouldn't compare it with Skyrim.. that's a totally different setting. You compare it with Bethesda's game in the same setting; FO3.