You bring up a good point: why is success considered a core component of individuality? Some of the most 'successful' regimes in history have not been all that individualistic; some in fact have tried to stamp out individuality. What's more, some of the most successful individuals are not at all ideologically independent - the odds being that if they were too independent they'd want nothing to do with 'the system'. So how did 'success' get wedded to the concept of individuality?
Well, since I think individuality is related to espousing an ideology, the quality of individuality is related to the degree to which the person succeeds in actualizing the ideology.
For an individualistic businessman, success is manifest in finances; for an artist, in recognition; for a politician, in persuading people. Of course, you can also be successful by simply "living the ideal", but that's a bit harder to measure, as there's a lot of unsuccessful people acting in the guise of individuality but are really just members of a subculture of showy different-ness. The hippie/new-age bandwagon, the punk bandwagon, the emo bandwagon, they aren't indicative of individuality as much as alternative groupthink.