There are a lot of things I criticize about Fallout 3, both as a game and as an addition to the series, but one thing I think they hit the nail on the head with is radiation.
With Fallout 3, it really FEELS like radiation is a factor in everything, something I got the impression that Interplay wanted, but left out. This is evidenced by the weapons dealer in Old Town (forgot his name) talking about how pretty much everyone has some degree of rads in their system. Not to mention we had an entire stat devoted to rad resistance, and for what? The Glow, and that's it.
But in Fallout 3, the food is irradiated, the water is irradiated, there are numerous hot spots throughout the map (though I would have preferred the water to be easily purified like in the originals). Bethesda screwed up the canon and in some cases basic logic, but I think they did a good job with radiation. At least, better than Interplay did.