If you say, "I feel friendly", you are saying, "I think that I am friendly." You could say, "I feel you are very friendly", but it would sound a little strange. If you're okay with being somewhat informal, "You're a friendly sort" could be a nice thing to say.
If you think that sounds kind of flat, you could elaborate. You almost need to know exactly what specific behavior you're complimenting, e.g. is he being cordial, mellow and easy-going, or compassionate, loving, and understanding, etc. "You're amiable" or "You're likeable" or "you're a very kind person" or an almost infinite number of similar sentences would convey the idea that you are happy with the other person's overall disposition (with somewhat varying connotations); but to address their friendliness to you specifically rather than overall agreeableness, you'll almost invariably need to construct the sentence to accommodate inserting "to me" at the end. "You show a great deal of patience and kindness to me, and you've ever been abundantly and amicably affable and amiable in your dealings with me." (Well, perhaps that's borderline on repetitive, but that seldom hurts in getting a point like this across.) The only problem is that you'll find people like me who haven't read the dictionary all the way through, so use words starting with "a" in case they made it through the "a"s. :)