I've never saw Sherlock as an unhappy character at all. Do people confuse intense concentrative effort with unhappiness? Or frustration or disbelief, because apart from those three emotional states which people might think displays Holmes "unhappiness", I don't really see it. John accepts that the way Sherlock acts (which to some would seem rude) as just the way he is, that's what true friendship is. John himself is unconventional to an extent, so why do people see them as some kind of "odd couple", they compliment each other perfectly, and fulfil each others social needs, so what is the problem? Sherlock's irritability and insults are almost exclusively turned on himself, *cue mental image of Sherlock pacing around the room berating himself while John looks on concerned and knowing that in a split second he might be dragged out the room with Sherlock on an obscure hunch*. I think that so many people are so used to one dimensional cookie cutter characters and relationships in modern books/TV/films that they just don't get the dynamics of anything that isn't stereotype cookie cutter.