As a Fallout 2 fan, I can only describe Fallout 3 and 4 as the guy on the right.
New Vegas was great though.
I liked the original Fallout games a lot when I played them but as far as I'm concerned there's Fallout 1 + 2, then Fallout 3D 1,2 and now 3. They're games in the same universe but they're so different that considering them to sequels skews how you look at them. The best example off the top of my head is AC: Black Flag. It was a ******* awful AC game, and every part of the game you played as an assassin sucked. So very many trailing missions... But, as a pirate game? It was brilliant, probably one of the best ever. That's how I see the FPS Fallouts.
Now, if you think of FO3 as FO3 then it's pretty bad. It's a bad like Broken Sword 3, in that changing to a 3d engine broke so much of the game and they didn't do nearly enough to compensate. I'll hold my hands up here and say that I wasn't the biggest FO3 fan and having played it again recently it hasn't held up well. But, I still see it as FO3D1, which is why I find its many issues forgivable. It was a bold jump into a new world and they didn't adapt well. FO3D2, aka New Vegas, was much better, even if it had its flaws. The big test for me has been FO3D3, aka FO4. Honestly, it's pretty incredible. They've actually built a world this time, the kind of world they have been lacking since Morrowind. It feels immersive, it feels real, there's a lot to stumble upon and just enjoy exploring. Is it rough around the edges? Yes, it's still a Bethesda game, but everything I find lacking is something that a mod will later fix and that was the massive issue with FO3/Oblivion/Skyrim for me: the world was so ******* bland and empty that you just couldn't make it all better with mods. The setting itself was ****, and no amount of water physics and rope arrows and Thomas the Tank Engine dragons could fix that. They ****** up the core of the game.
This time, they not only haven't ****** it up, but so far it feels like they've nailed it.