Maybe. Maybe not.
It feels like, even after all the years in development, the game doesn't have as much content as Skyrim did. It's like Beth cut every corner they could by;
-Only making 1 real city, but giving us the tools to make our own
-Only making a handful of weapons, but relying on a borderlands-esq system to make many more
-Not making many quests, but having infinite generated ones
-Using a limited dialogue system so they didn't have to do as much writing
I like the game, but it feels like they really gutted it compared to previous installments. Personally, I hate the reliance on generated content as many of the guns feel the same and the radiant quests become dull extremely fast. IDK, something about it just doesn't feel like Fallout. To me, it gives off the vibe that it'll be popular for a short while, but then fade away once something new comes out.
They turned Fallout into an FPS, closer to something like Farcry than to what it once was. But Beth owns the IP, so they can do with it what they want :/ I'll always have mods.
(No, I'm not a dinosaur. Didn't care for 1 or 2, loved 3, and greatly enjoyed NV)
But back on point; Do I think it's a legendary game? No. It's good, but I don't think it outshines the previous installments. Maybe after the DLC and some mods my opinion will change.
EDIT: Everything Taramafor said above