Yes, it is very normal for you to be interested, even obsessed, in large cocks. After all, those are the ones that you want to be shoved up your wife's pussy!
Although many will disagree with me, and in a very loud voice, I do believe that a part of being a cuckold is "experiencing" the cock that will fuck your wife, in a number of possible ways. It is very normal for the cuckold husband to want to see, touch, even suck the cocks that fuck his wife.
I could even go so far as to say that the cuckold husband wants to experience the cocks of other men but cannot admit it to himself, so he offers his wife's pussy as a substitute for his own mouth. And while he is watching the other man fuck her, he is experiencing much of what he would if it were his mouth instead of her pussy.
I expect to get some strong protests to what I have said, so let's hear them!