There's no doubt that Ennis loved Jack, had a strong love for him, care about him deeply, felt a connection to him like no other. I mean, if it were just a "good sex" thing, do you think it could have lasted 20 years? That I doubt. But whether he says "I love you" or not in the closet scene is a very interesting question. I will have look closely and listen too. I know, in the book it just says he inhaled trying to get some sweet smell of Jack, but there was nothing left... or words to that effect. I'll get back to ya, after I see that scene again.
R