Narcissism: "extreme selfishness, with a grandiose view of one's own talents and a craving for admiration, as characterizing a personality type."
Self-confidence: "a feeling of trust in one's abilities, qualities, and judgment."
I agree that any good president - in fact, any good leader - needs self-confidence. It is likely nobody running for president lacks it. Where one crosses the line from self-confidence over to narcissism is a debatable issue.
The thing about really good leaders, however, is that they subjugate any overt narcissistic tendencies and instead spread credit liberally. Anyone who has worked for multiple bosses will likely confirm that the ones who give credit to their subordinates are "better" bosses than the ones who stress what they themselves did.
It seems a fair criticism of Bush II to observe that he was oblivious to poor performances in his administration. E.g., "Heckuva job, Brownie" was indicative of that type of failing, not narcissism.
It seems a fair criticism of Obama and Trump to observe that both have grandiose views of their own talents and a craving for admiration.
Whether any given president or presidential candidate crosses the self-confidence/narcissism line is probably in the eye of the beholder. It would be interesting if folks could cite announcements by other presidents analogous to Obama's Bin Laden one and compare the "I ..." phrases to "they ..." phrases. E.g., when
Truman announced the atomic bomb, the only two uses of the pronoun "I" occur in the last paragraph, and even there in the context of Truman making recommendations to a Congress that would make the final decisions.