It helps, but it's not exactly necessary. Due to constantly changing script writers and voice actors, the series has some inconsistent character development. Also they really only mention the previous games in passing. The recent games in the RE series seem like mostly self contained stories.
Edit: I'd like to add that I still recommend playing all the previous entries simply because they're just all around good and fun games
PSN: spacedirtyjerz Currently Playing: Resident Evil 3: Nemesis, Zelda: OoT, Sonic's Ultimate Genesis Collection, Conker's Bad Fur Day, Black Ops II