What did FO3 do right? Well, you could take just about everything I said of the game, shortly after its release,
in my Fallout 3 review that I posted years ago, but then re-posted again on this site (Page 19, 6 posts from the top) and considering I was overall receptive to it at the time, that's a good place to start. But, for those who value brevity, I can take out particular snippets for this topic, instead.
"In the ashes of Brotherhood of Steel, 4 years later, comes Fallout 3! In the wake of such a tragic bombshell, this title has ONLY room to improve. So, from that perspective, this game has done nothing short of fulfilling the emptiness in our souls that many of us Fallout fans were left with, after BOS."
"Unlike Fallout 1 or 2, armor gives your character various skill boosts, here and there. A jumpsuit might enhance your repair skill slightly, while a pre-war business suit would enhance your charismatic sway over people. But wear these out in the field in the heat of battle? Surely not!"
"The VAST menage of outfits you could adorn yourself with, the infinitely unique appearances you could generate for yourself (well, close to), being granted such a wide variety of aesthetics is hardly a bad thing, at all! Sure, my damage resistance may suck, and I have no combat bonuses whatsoever... but c'mon! A raider just got slashed to pieces by Freddy Krueger!!!"
"While it provides no challenge to your average gamer, and definitely zero for a Fallout veteran... Even though it merely simulated the SPECIAL system, and none of the stats had much of an impact on your character... Despite the fact that the voice cast of hundreds of Wastelanders seemed to be comprised by all of FOUR voice actors... Although every single ghoul, and every single mercenary, and every single Mutant sounds alike, with no audible distinction from one another... Fallout 3 is fun. It may not have NEARLY as much replay value as its predecessors, but as you've doubtless been able to gauge by reading my review, I played it A LOT!"