I don't think any of us can convince your wife to enjoy oral sex as much as you do. Some women do, some don't. Most do enjoy the pleasure of your partner. Like all things, communication is key for this and I think you just have to express how you feel.
If you've ruled out that she might have had some unpleasant or traumatic earlier experiences, it's possible that she is simply too self-conscious to find oral sex that enjoyable. Some women have trouble imagining that the scent and appearance of the genital area is attractive.