Why are Harry potter and Tw*l*ght always compared?

Because people want to. Why compare Lord of the Rings and Harry Potter? Or Buffy the Vampire Slayer and Twilight? Those don't have very much in common either, and yet they're constantly compared. Because people want to compare them.

Things don't have to have lots of things in common to be compared. And, anyway, they have more in common than "they're both popular young adult series." Both have been translated into over 30 languages, which means they have touched millions - if not billions - of people's lives. Both carry heavy messages (that can be interpreted as good and bad) and have characters that people consider role models and characters that people look down on. Both have writing styles that are unique. Both have won awards and been turned into movies, both have symbolism, and both are great stories. Both have accumulated millions of loyal fans (of all ages).

Because:
1) this is a Twilight vs. harry Potter fanspot
2) there was a Twilight book cover that said "move over, Harry Potter" on it
3) they're so far the only two book series that have sparked such massive popularity and attention from press and fans alike
4) Robert Pattinson played a role in both franchises
5) Media constantly compares them to each other because of their popularity, thus reigniting arguments from both sides
6) The authors are both women of about the same age and wealth (?) which sort of makes them comparable
7) They both feature and are directed mainly towards young adults

IKR.
I think that it's the fact that Robert Patterson (I spelt it incorrectly, I know) is in both. Not sure.

I don't know I do it because i think debating is fun.

Because it's possible. You can compare anything to anything if you want to.

People choose to because they are both fantasy novels, they have similar fanbases. They have ad similar impacts on society aand media.

Because they were two of the best series... and robert pattinson was in both...? not sure but people can go waaay over the top with this stuff! and im like, calm down, its fictional O_O (btw i like twilight ^^)

Because Harry Potter fans and Twilight fans always seem to be the most passionate about their books, therefore their unwilling to accept that people prefer the other, it's blasphemous I say!!

They are compared because the people want them to be compared. I am not sure why, though.

Potato told us to compare them.
Potato is always right.