I said Fallout 3 had a pretty weak story. 1, 2, & and New Vegas all have fantastic stories and writing.
The game is pretty violent and dark, though. Every game in the series is rated M and for good reason.
If you want more information on the game, here's the TV Tropes article:
http://tvtropes.org/pmwiki/pmwiki.php/VideoGame/Fallout?from=Main.Fallout