Its not about ease, a good riddle should leave you pulling your hair out not being able to think of ANY answer that fits, and then when you hear the answer you should groan at how bloody obvious it was and wonder why you couldnt see it, or in those blessed moments of figuring it out it should all click into place as the answer fits like a key and leaves no doubt in your mind: I am right.
A good riddle doesnt use word play or rely on obscure knowledge, but takes advantage of the way a person thinks and exploit blind spots on common thinking.
Riddle me this (this isnt my riddle, but a favourite from my childhood):
There are 3 figures climbing up a hill, the 2nd figure is the son of the 1st, the 3rd is the brother of the 2nd, but the 1st ISNT the father of the 3rd, how is this possible?