Help My Son Eats Only Plain Rice

I have a daughter who's 5 yrs. old who eats fantastically. She eats almost any food we serve her. Then I have a 3 yrs. old son who's quite opposite of the sister. He's very picky and during mealtime he only eats plain white rice. I tried giving him veggies, meat, fish and soup, but he won't eat them. Remembering the old days when my mom or aunt would forcibly let us eat veggies and fish, it was unforgettable... But those where the days which I don't want my child to experience, because I feel there's a better way to handle such situation. And when it comes to sweets, biscuits, cookies (He loves Oreo by the way) and pastries I have no problem, he even eats faster than the sister. Though I minimize giving this type of sweets, as they don't provide the kind of nutrition their body really needs. So what I did was to read articles regarding picky eaters and tried some of their recommendations. One of which was I tried mixing the steamed fish into my boy's white rice thinking he will never notice it since both we're white in color. Instinctively, the moment he puts the rice inside his mouth he was able to recognize the taste, so he right away remove it from his mouth and quickly drinks water to wash it off. Then the other thing was to cook the food in a colorful way, but no avail because his taste buds were not adjusted to the new taste. So what to do? For the moment I don't know, but as long he eats rice, noodles, some fruits and drink his milk he’ll be ok. Because sooner or later he will need to eat all these stuff to satisfy his appetite as he grows, just like me when I was a kid... Any friendly advice or suggestions? Because I still want to give these healthy food to my kids.