Remember, infidelity is a SYMPTOM, not the cause of any problem. This may explain why you feel this way! You do not feel that your relationship is better BECAUSE of his infidelities and your subsequent dealings with the problem, but because the symptom showed you first of all that something was wrong, and second of all lead you to action, to rectify the situation!
Had he NOT had an affair, he would have been unhappy, without showing any outward signs, and you may never have gotten to the place you are now!
Like many diseases, you were able to figure out the cause by examining the signs...and caught on time to be able to cure it. You did not only take care of the symptoms, but of the cause of these!