[quote=Blitz]
(Which confuses me because Sora's Keyblade is supposed to be Riku's... but whatever.)
[/quote]

It could be argued that Riku was originally denied the Keyblade because he gave his heart over to darkness, but Ansem's (or Xehanort or whatever) influence, as well as the actions after KHI and during COM and II, gave him the ability to wield the Keyblade again :T

(Sorry for all that, my Internet's being stupid =_=)