They have incredible chemistry together which cannot be denied...but he's supposed to be all 'bad' and 'dark', even for a vampire. Technically he's all 'wrong' for Elena, but he loves her. She brings out the best in him. He trusts her. All the defences he's built up just crumble when he's around her. It's so much more profound than SE, which is more of a 'high school romance with a vampire' story. I get that people love SE, because it's safe. Stefan isn't as dangerous as Damon is, and when Elena met him, Stefan's humanity was firmly established. Damon was wilder, not hesitating to kill people, even when he didn't really need to. There's an element of the 'forbidden love' to DE which is absent in SE, and people love that kind of story. Also, SE were together by 1x10, and they've pretty much stayed a couple ever since. I'm not denying that SE don't love each other, because they totally do, but frankly, they make a boring couple. DE have such intense scenes and amazing chemistry, but they're not together. And that makes people want something to happen between them and for them to get together even more. Because SE are a couple already, there's no waiting involved. It's pretty straight-forward. I think the wait makes DE even more powerful.
I think to many people Damon's love for Elena seems deeper than Stefan's love for her simply because Damon knows he can't have her, and he's willing to accept this to make sure that she's safe and happy. It's the definition of selfless love, and it's so amazing coming from this guy who has been hurt so badly by Katherine that he's willing to let himself suffer again just to make sure the woman he loves is happy.
It's also a reflection of what I think many people love about Damon as a character. He's such a closed off, typical "bad boy" sometimes, yet he still has the capacity to love so deeply. He's will to spend 100 years planning to rescue a lost love, and then sacrifice his own happiness watching the woman he loves love his brother because it's what she wants and what she thinks will make her happier (though I doubt that, I mean, look how much Damon is willing to sacrifice for her.)
Also their relationship itself is so strong. They're bonded by heart ache and losing the ones they love and going through some horrible experiences. Elena brings out the best in Damon, showing him that he can let people in and show the world the compassion he has about the people he cares about, and Damon gets the more serious side of Elena and her issues about her parents and her little brother. They're both a little bit lost, and they sort of help each other find their way, versus Stefan who relates to Elena on the broody level, but hasn't necessarily gone through the heart break Damon and Elena have.
To sum it all up, I think always claims he doesn't deserve Elena, which really adds to the fact that he does. Damon has been willing to give up everything for the woman he loves, he's reunited with his brother, and he's trying to move forward and be a better person even in the face of everything that's gone wrong for him. He needs Elena and the happiness it would bring into his life, and I think anyone who's ever give up something to make someone happy or wondered why they're never the happy ones relates to that. We route for Delena because we want to believe that people can be rewarded for trying to be better than they are today, and because we like to believe that love concurs all, even a rough past and a broken heart.
Because when two people fall in love, they fall in love so deeply. I believe true love is what Delena would have if they ever became a couple because. Damon and Elena are best friends and they know each other so well. Elena knows how to bring out Damon's humanity and Damon brings out the fun and lighter Elena. They would be there for each other no matter what and that is why their love is true. :)
I think it's because Delena have a forbidden element when it comes to their relationship. Damon is the bad guy, rips people to bits, void of emotion, manipulates and even attacks her best friends and all this just screams that she should not be with him.
Yet their scenes are just magical. They come to life. They buzz with electricity whether it is something good happening or bad. And it just feels like they're meant to be, regardless of what happens. They're constantly drawn together even though the odds are against them. Despite all the awful things Damon has done, this monster, Elena can still see the real Damon Salvatore.
That's why Delena have more fans. It's not the typical "boy-meets-girl" scenario. They bring that edge to the table that I have yet to see.
i do thk delena would work better coz as much as he's the bad guy,so wild less of a human,sucks out life from people he still adores elena & he says ''she's the only one he can count on as afriend'' and i believe that its from friends that we get sweethearts coz we know their most inner feelings & from this demon can light a frame of love in elena's heart and it will become wild than stefan's.demon charms elena & there is alwaiys asmile & giggling so the chemistry between them is intense and when they look into each other's eyes theres a tension that alwaiys pulls them close which means we are meant to be