If this came out today..
.. If this exact move came out today, and let's say, hypothetically, had the name David Fincher or Christopher Nolan (or some other trendy director) attached instead of Cameron Crowe, it would have a rating of AT LEAST an 8.
Vanilla Sky is a brilliant movie with some wonderful performances, a killer soundtrack and some unique ideas. It's just a shame it came out during the early IMDB days, when 'twist' movies were saturating the industry. That plus people's disdain for Tom Cruise, who actually did an amazing job, are most likely the reasons it's failed to find its audience.
I just compare it to Inception, which is a fair comparison since they're similar thematically, and think wow, Vanilla Sky actually had a lot to say. Inception, while fun, really didn't.