I like animes some-what you love on first minute of episode 1, like beelzebub.

But sadly, it's getting shitty when you've watched all 60 episodes 5 times.

I want something that has demons, humans who are '' warring ''. Fighting, demons, and so on.

Blood lad is pretty much beelzebub like. Except it doesnt really have school life in it.

If its demons and whatnot you're after you should probably watch;

-Full Metal Alchemist (either one will do)
-Ao no exorcist
-Hayao Miyazaki Films
-Inuyasha
-Madoka

Thats the ones on the top of my head, I'll post more if you want

i'm pretty sure you gonna like ao no exorcist(or named blue exorcist too)

My top 5

1.Code geass
2.Death note
3.Fma Brotherhood
4.Marai nikki
5.Samurai champloo

All legendary anime.

I started watching ao no exorcist, it's good enough to I could spend time to watch it :>

Right now i would say for you would be great.:
1. Ao no Exorcist
2. Soul Eater
3. Blood lad

When you said Demon you know what come to my mind
Highschool DxD

~ Soul Eater, it's a must. (Funny anime with lots of action and a good plot)
~ Shingeki no Kyojin, this anime will knock you off your feet. (Action, supernatural, it has giants eating humans who're fighting for survival and stunning plot twists)
~ Fullmetal Alchemist: Brotherhood (This anime has the best story/plot by far it's gut wrenching and it's full of action.)

And as Jingles said, Miyazaki has some amazing films. My favourite is Spirited Away.

The best Miyazaki movie might be Howl's moving castle though. Well, they are all great so just watch them all.