Well Jenny, you probably get along so well because he is Gay and Gay men do tend to be more open with feelings, no need for macho behaviour, he probably wears his heart on his sleeve, so you can talk, confide and interact with him more easily than a Hetro man.
The long and the short of it, is that he IS Gay and you can never have the kind of relationship either of you would probably like. It would never work and neither of you would be happy. Try to be grateful and satisfied that you have such a wonderful friend and don't spoil things by admitting your true feelings to him.
As you are at University, I'm guessing you're still quite young and you have your whole life ahead of you. You will meet that special person, who you'll settle with and have a family, but understand your best friend is not that person.