Having been disappointed by Fallout 3, I found myself looking for a similar game which is more fun to me. Now where do I find a more fun post-apocalyptic shooter/roleplaying game hybrid? Turns out I had already bought that game during some previous sales on Steam: Borderlands. So I spent most of the weekend playing Borderlands, and I was having a blast. The combat is more fun and varied, because now different weapons actually require different tactics. Instead of useless junk I loot only things I need. And instead of my weapons getting worse all the time due to wear and tear, I now get constant weapons upgrades. There are as crazy characters in Borderlands as are in Fallout 3 (albeit not so many), and the main story isn't any worse either.
Apart from the combat system (where Fallout 3 has no excuse), I can see that the main difference between Fallout 3 and Borderlands is that the former is mainly designed as an immersive virtual world, while the latter is mainly a game. Borderlands is more fun because it is *made* to be fun, and not designed to give an accurate depiction of a post-apocalyptic world. Which is all fine with me, I didn't find Fallout's vision of how a world after nuclear war would look very believable in the first place. I can see that weapons degrading is somehow more "realistic" than finding them as loot even from enemies that aren't using weapons, but "realistic" often ends up being the same as "tedious".
If I want to explore a coherent, realistic world, I turn off my computer and take a walk. Any virtual world in which I am a hero is by definition already unrealistic. So I'm really not all that worried about how immersive a virtual world is, as long as it is fun to play. The cell-shaded graphics and over-the-top whacky boss mobs of Borderlands are more fun to me than the realistic eternal grey-tones of Fallout 3.