As mentioned above, that depends on what you wish to study after you graduate from high school. Different universities excel in different fields and it would be a good idea to think about what you wish you to study beyond the HSC prior to thinking about universities.
In terms of examples of what field(s) each university excels in:
Medicine (including related fields):
Studying Medicine is generally thought not to be affected by the university, meaning your main goal in that case would be to determine the university that offers Medicine at which you wish to study, as well as meeting all entry requirements for medicine at the chosen university.
Universities that excel in Nursing include WSU and UTS (although I believe nursing is similar to medicine in the sense that the university you choose to attend is not a crucial factor).
Universities that excel in Psychology include USyd, UNSW, MQ and WSU.
Law:
People generally seem to lean towards Go8 universities like USyd and UNSW for Law due to their prestige. However, it is important to keep in mind that a career in Law is competitive, irrespective of the university that the student attends.
Engineering:
People generally seem to agree that UNSW is the best university for Engineering. Universities that also excel in Engineering include USyd, UTS and (potentially soon) WSU.
Business/Commerce (including related fields):
This would depend on what you wish to specialise in within your Bachelor of Business/Commerce. Universities such as USyd, UNSW and MQ tend to excel in finance and accounting majors, whereas WSU tends to excel in majors involving psychology/sociology, such as management and human resource management.
In terms of other degrees such as a Bachelor of Actuarial Studies, universities that excel in this field are MQ and UNSW.
I hope this helps!