"This is, of course, a slightly wild thing for the studio that made Morrowind (its actual best game) and Skyrim (its most popular game by miles) to say"
FO3 did some thing much better than NV. NV is the best written, by far, but it's different, not better, for gameplay. FO3 was closer to the original games in gameplay. There were a lot more random events while traveling, and they could react with each other in really unique ways. NV essentially removed this. There are a lot of other areas of difference too, but NV always gets remembered as better, and I think that's largely because the things FO3 did better are systemic, so less noticeable, while NV had better stories, which you have to notice.