Maybe because gamers these days have different expectations?
This is I think, one of the more sensible posts in this thread.
Gaming has eras and changes just like every other industry. Remember when Space Invaders was the big thing? A lot of fans of old Atari games probably felt the way we do now when the mid 80's to early 90's rolled around introducing these new non-arcade style video games like Ultima, and King's Quest. They weren't right or wrong, they just had certain expectations and beliefs on what a video game should be, and RPGs and Adventure games didn't really fit into those beliefs. Why would you play a game for story, or just to waste time wandering around solving puzzles? If you want to spend your leisure time playing video games do something fun like blowing away aliens on an Atari, or in the Arcades. Puzzles and managing food while wandering around dungeons isn't fun!
So the mid eighties came around, and up until the late 90's-early 00's (2000's?) we had a large amount of fairly intelligent games, some with exceptional story telling. Fallout was of course one of these games with its deep RPG statistic system. The Atari Arcade crowd that shunned the "evolution" of the industry would have likely shunned Fallout if they played it, while some of the more casual and easy going gamers from that era may have very well loved it if they didn't focus on what they think a video game
should be.
So what happened with Fallout 3? It's a cycle, we're now in an era where arcade style games are more dominant like they were in the Atari era. There are certain things that will never come back in style such as monochrome graphics and beeps and boops for sound effects, but Fallout 3 is more or less trying to appeal in an era where quick action for kicks and giggles is more popular than "deep gameplay". I'm sure that one day games like Fallout will be on top again, with prettier graphics sure, but is that really an issue? Maybe Fallout 4 will actually come out in an era where actual role playing is back on top, I wouldn't hold my breath for it, but it's a nice thought.
I don't think graphics are really responsible for the current state of gaming, you can make deep games with fairly pretty graphics... look at Supreme Commander. The issue lies in the fact that Space Invaders is what's popular now, not Ultima or King's Quest. That's why Fallout 3 places more emphasis on action than stats. Just be patient and we may very well see the return of games with more depth in the foreseeable future.