Personally, the sequel was 10 times better then the original. Sure, the first one was good, but it was just simple and dry. No magic, no nothing, just a straight movie about following your dreams.
This movie was so much more complex and more grown up. It was definitely more realistic. If it were like the first one, of course Troy would have never given into Sharpay's world. But this one shows more reality. He does give in and lose himself because money and opportunities show up. In the first one, you see the relationship between Troy and Gabriella begin. But in this one, you see them in love with each other and that love having to withstand trials.
I think the acting has gotten way better. The actors seem more confident and the chemistry is better then ever.
The songs are more modern, making it more enjoyable. It's really music you can dance to. The movie is more like a musical because in the first film, the majority of the songs were songs that were to be performed. These songs are more like just "randomly bust into song and dance" then the other one- making it seem more musical. The choreography has been stepped up a lot as well.
Visually, the movie shines. The backgrounds and the colors are brilliant.
The movie is definitely amazing.