"Narcisstic tendencies" is a very common smear / throwaway labelling we hear a lot -- about bosses, exes, manipulative relatives and what not. In some cases it's valid, but in most it's simply not. Unless you can point to specifics, we'll have to include this labelling of Snowden in that category as well.

But even if it did apply -- it would also be perfectly consistent with the possibly that he simply considers himself a fearless do-gooder. I don't rule out your alternatives, but Occam's Razor (combined with the fact that there's no visible evidence of him having profited in any way; and his general bearing and demeanor do not correspond to those of the publicity whore type) does favor the former.

(Not to say that he is or is not a fearless do-gooder; just that it's not at all unlikely that that's what he considers himself to be).