Whatever you do, don't ask her directly like half the guys in this thread are suggesting. Few things are less attractive than a guy who's all worried that his wife is fantasizing about some other dude. The vast majority of women are actively turned off by nagging, begging, insecurity, etc.
Positive reinforcement would be a good place to start. Don't pick something weak like, "Thank you so much, honey, the other night was wonderful!" Try something a little dirty and shocking, whisper it in some mundane situation (like when you're cleaning up dinner), then move on like it was no big deal.
In the long-term, though, you'd be well-served by getting a better handle on what makes your wife tick and learning how to properly seduce her. Much of the time, something like "bad taste" is just an excuse that means you didn't turn her on enough to make her stop caring.
Try reading The Art of Seduction (Robert Greene). It's a little long, but Greene uses a lot of good historic examples, breaks people down into types, and generally makes it easy to figure out why you're not getting the results you hoped for.
It's easy to say that your wife should be more cooperative, put in more effort, etc - but if you want a different sex life, somebody has to change and it might as well be you. There's a very, very good chance that with a change in approach, you could have the sex life you want.