Ok; i don't actuallly a huge fan of Obito but "friendzone" crap is bullshit.
First off; it is the feeing of "love". Don't know if you can comprehend with it. Someone can love a friend, a family member or a suppose. Love is not simply the need for having physical contact. Obito loved Rin. That's it. He lost the loved one; and his eyes opened in the view of "ninja world"; what people can do, kill, have or lose.
And there is no comparasion of pain there. Pain can't be compared; everyone have it different ways. So "Naruto's past was more painful; so no one can say shit about him" is a flawed idea to begin with. He just says they also had a sort of pain.
And you say "a girl who does not even love him"...She was a person who are being really nice, friendly, kind and good to Obito. It was obvious she cared for him. And the matter is; Obito did love her. It might be one sided in terms of romantic interest; that does not mean Rin was a careless ***** and Obito should not love her.