Both twilight and harry potter are very successful, especially among teenagers. Some people keep arguing about which is better, though in my opinion, THEY SHOULDN'T BE COMPARED!
Now, i have to admit i love both series! I'd say harry potter is unisex and appropriate for all ages, whilst twilight adresses mainly to teenage girls. HP talks about friendship and love, while twilight is more romantic! Also, hp gives lessons of life, although maybe in some cases, i would prefer reading twilight.
Finally, They are both written by two very talented and imaginative writers, j.k rowling and stephenie meyer. They wrote these books to give teens (and not only) inspiration and time of happiness. So, if you don't like one of these two series, don't blame them! We can't all have the same tastes!