I love Harry Potter because it not only taps into themes like good vs. evil, but it requires a knowledgeable depth of Latin and history as well (does the name Remus sound familiar? No? Well. Go brush up on your basic Rome facts).
J.K. Rowling created another world. Twilight is just a simple love story. Love stories don't generally rely on intricacy when it focuses on the one subject.
They're just two books on two entirely different levels of literature.
Personally...I have never read Harry Potter. My friend convinved me to watch the first Harry Potter movie and I fell asleep. JK Rolling is an amazing writer from what I have heard, but I will never read her books. Her subject does not appeal to me.
Twilight has a simple writing style and simple imagery. However, I love the characterization. I would pick Twilight over Harry Potter every single time because the story has qualities that appeal to me.
Twilight was not written to be compared to Harry Potter. They are both unique stories. Just because Twilight is not as well written as Harry Potter, does not mean it should not be read.
I like Harry Potter more, but I do have to say that I've never read the Harry Potter books in English. I picked a copy of the first book up and began reading it- I stopped after five pages. It seemed too easy to read, if that makes any sense.
Even so, I do enjoy the series. I have each book in German and in English, although I haven't really read the English ones.
I love Harry Potter and Twilight but I have to say, Harry Potter is much better. It's written better and has a better plot, better characters, etc. Both are good but Harry Potter just has more to it.
I have to say, Harry Potter isn't really an original theme- just like Twilight. Harry Potter is a classic story of good vs. evil where good triumphs evil time and time again. Twilight is a pretty classic love story.
Personally, I love both series. I prefer Harry Potter because it's suited for a wider market. Twilight was written for middle-school to early high school aged girls. Harry Potter was written for older teens.