Not really a complement, but just being referred to by someone as a friend is nice, plus, it's so passing it can't really be insincere. One complement I actually despise getting is being called smart. One, because it's incredibly vague, and two because it makes me feel like the person who said it sees some disparity in the way we perceive the world. Generally, the smarter you think someone is then you, the less capable you feel you are to sympathies with them. But a friend, by their nature, you sympathies with.