I find Fallout 1 and 2 to be remarkable in the sense of what they offered and the scope of the series at the time and I commend Obsidian for what they did, with what they had available to them and the length of time given to bring out the New Vegas IP they did very well. I find that Bethesda haven't done much good for the series lore wise and in most aspects have absolutely ruined it with the dumbing down of RPG elements, plus their abysmal storytelling... but it's opened it up to greater audiences I guess... I finished Fallout 4 once and was severely disappointed in it.
I'd have to go with Vegas as it's the closest game that would match Fallout 1/2 in all their glory and it's somewhat well modernized.