When he was two, our son really seemed to dislike bananas. We kept pushing them, because they are an inexpensive and healthy snack. It took probably 4-6 months of having him try one at least once or twice a week, but now he loves them.
The key, in our house at least, is that the kids are required to try everything we put on their plate (at least 1 bite). If they don't like it, they are welcome to spit it out on their plate and not required to finish it; but we do require that they try it before they can leave the table. Just as with any other rules, you have to be willing to stick to your guns and not give in: make rules you believe in, and enforce them 99.99% of the time. (The .01% is reserved for public outings or special occasions where you don't want to make a scene, like Christmas dinner.)