1, 2, and NV all excel at different things in different ways that I don't really care to try and pick which ones better. They're all just excellently written games for what they're trying to do. They all featured very well executed overall narratives as well as larger world building that feeds and builds off each other resulting in a rich and interesting setting. They all do an exceptional job of presenting this exaggerated depiction of America and what a post nuclear setting there would look like and how it could actually develop and attempt to recover in the aftermath.
3, 4, and 76 are just not good on a basic level. They're all pretty terrible for what they're trying to do, especially so at developing the setting and building on what came before them and the premises and ideas that were explored in prior games and making that world feel consistent and believable. That said they're not devoid of good writing, there are plenty of individual quests, characters, and bits of lore that are quite good. But from a larger narrative/story telling perspective they're just kind of messy and half baked at the best of times.
