Sometimes, if you keep eating something regularly for a long time, it starts tasting better. I don't know if it is just a power of habit (familiarity feels pleasant) or whether your brain gradually redefines "food" to mean the things you eat most often (so your desire to eat becomes a desire to eat a set of specific things).
As an experiment, start adding one fresh tomato (cut to pieces) to every meal you eat. (OK, not literally every meal; I wouldn't eat a tomato with a sweet pancake. But if something contains meat, it can contain a tomato, too.) Do it for three months and observe what happens.
If tomato does not work for you, experiment with other vegetables, find one (or a small set) which works for you, and then use it consistently. And always have enough of them at home. Remember that every successful diet starts in a shop. (If you don't buy them, you cannot eat them.)
As shminux recommends, spices and dressings are your friends. The goal is to make yourself eat vegetables, not torture yourself with something you don't like. But if it works, you may gradually need less of these ingredients.
I think that the nutritional value of the food, or at least the perceived nutritional value of the food, also plays a role in how quickly you start liking it. I've started liking raw beef liver and fish oil after waaaay fewer tries than say, ceviche.
I have a strategy for getting myself to eat vegetables. I've been using it for about six months now, and it works well:
Side effect: people who see my plate think I'm a very healthy eater. But sometimes they ask my "why is your salad steaming?"
I also posted this on my blog