You are choosing to make life miserable not just for your wife, but also for yourself. Most of our unhappiness is due to our own attitudes and mind-set. If we try to change our own perspective of looking at things, we can alter our emotions too. By continuously telling yourself that your wife is not good-looking or smart, you are not only making her feel unwanted and inferior, but also feeling inferior yourself.
Each individual has some positive traits and some shortcomings. Good looks are subjective judgments, and good looks definitely do not ensure a happy marriage. Several dark-skinned persons have been renowned beauties. You may not be perfect yourself! Try to focus on her positive qualities, for example her smile, her cooking skills etc. By respecting her, praising her and treating her with love, you will yourself see the difference in her facial expressions and behaviour. She may even feel motivated to improve her looks and smartness. On the contrary if you continue berating and ridiculing her, she may lose her self-confidence and may not want to make any efforts at improving your relationship. You have gone into this relationship willingly or because of your hesitance in calling it off at the last minute. It is now your responsibility to honour this commitment and make efforts to improve it. Remember that you cannot change others, but you can always change your own behaviour and attitudes. Try to make it a win-win situation, so that both of you emerge winners!