I'm not faulting anyone for enjoying any of the newer games (or even Fallout Brotherhood of Steel) but the tone is extremely different. You can call Fallout 3 bleak, but it's not bleak in the same way as Fallout 1 was.
<SPOILER> The entire story arc of Fallout 1 is that you are cast out into the lethal wasteland to save your vault (one of the first things you find is the corpse of some other unlucky guy from your vault), struggle against all odds, bring down an army of super soldier mutants and a fanatic cult that wants to turn all humans into mutants while what's left of the US military sits in its own little bunker full of high tech equipment but refusing to help you, then once you make it back to your vault your Overseer refuses you entry because you would no longer fit in with the community. The entire journey is basically the premise of Rambo First Blood. </SPOILER>
That's a lot bleaker than the gory ultraviolence in Fallout 3. BTW, Fallout 1 and 2 already had the Bloody Mess perk and ultraviolent death animations, it just wasn't slo-mo and first person. Those weren't what made the game bleak, though. If anything, that was intended as dark humor (cf. splatter "horror" movies like Braindead, ultraviolent "splatstick" comedies) and a nod to pulp fiction (cheap novels, not the movie of the same name).