https://youtu.be/x4TZEVqKIvs

To summarize:

Sharpay is actually a good and decent person who is one of the most well developed characters in the cast of all HSM movies; Troy is the world class self centered jerk kid.

Sharpay respects other people and is very welcoming.  She welcomed Gabriella to the theater club, telling her they loved new members and that even if she wasn't the lead role there was a role for her elsewhere in the cast.)

She puts so much effort into helping Troy potentially get into a D1 school on a full sports scholarship and doesn't ask for him to date her or anything in return, she just asks for him to sing with her. She got him a job at a her country club, got him able to talk to recruiters, gave him a chance to play with D1 players)

She is devoted to theater with a burning passion and wanted to go to college for it. When Gabriella gets the scholarship and spot in college instead, she decides to stay around and help the school's theater. 

Her brother betrayed her miserably in the second movie, and she STILL gives him all the credit for an award that she earned. 

When she wasn't announced as the lead in HSM1, she was content with her understudy role, wished Gabriella luck, and helped her out in practicing. 

When told she has to work her way to fame even though she could buy her way into it, she willingly accepts her place as an assistant, playing her cards wisely and working her way up the ranks.

Troy wants the world to revolve around him. The theater has to wait on him for recalls; he auditioned when he was told he could no longer. The first production Senior Year, he ditched the show to go hang out with Gabriella

He complains about money being an issue, yet when is seen working, almost always ditches work to mess around and abuses Sharpay's gift of "I can get you in and keep you in this job". He also gets everyone else off track in their jobs, potentially getting some of them fired.

He gets a full ride to a D1 school, where sports are everything (if you pick sports, you are that sport and that sport alone), yet expects that he'll be able to double-major. 

When given an offer to scrimmage with college players, his friends ask if they can get in. While the worst Troy could have done is ask and be told no, he instead disses his friends, insults them, and tells them no without even asking.