Pictures of Stanley Armour Dunham flashing his “big smile” look much like Barry flashing his “big smile.” Even though Malcolm X's “big smile is also similar, I prefer to go with Occam's Razor and stick with Grampa Stanley as the source of the smile, although appearance can mean very little when determining paternity it won't hold up in court.
The only resemblance I see between Barry and Malcolm X is the general shape of the head and the teeth, but none of the finer features look very similar to me.
The whole face shape and body is the same as the young Stanley Dunham.
There is a montage of Obama/Malcolm X images somewhere that asks people to guess which is which- the catch is that they are ALL malcom X