One Piece is more of a fantasy-style series that isn't meant to have the level of seriousness and drama as Naruto. Besides, characters that don't die in One Piece tend to reappear to contribute to the series in a meaningful way (ie. the ex-Baroque Works guys in Impel Down). When a character has a dramatic (or sometimes not-so-dramatic) death, they stay dead. The only exception I know of to this so far is Pell.
10/4/04 - 8/20/07