For me it does not matter if a top is short, tall, fat, skinny, hairy or smooth. A good top for me has confidence, and knows that a bottom is there to serve his sexual needs. That my mouth or ass is there for him to use at his pleasure. The top should be verbal enough to say what he wants the bottom to do, if it is to use tongue, mouth or just to lay there and take whatever he gives you. For myself I need a bit more adventourous top with a wicked mind that likes to expand and stretch limits, however without any phyical damage or injury. There is a fine line between pain and pleasure and the top that I need should ride it.
I think if a top had a history or experience in being bottom, he will know better what a bottom or submissive bottom needs. In the end it is about feeling, trust, openness, verbal communication, not physical looks...