the biggest problem with white rice is the lack of fiber, the somewhat high glycemic index, and it has the same problem all processed grains have: lacking potassium, iron and magnesium. these days though white rice and other processed grains all come with added b-vitamins (before that started at the turn of the century, there were massive b-vitamin deficiencies popping up everywhere). white rice has less protein than most grains but at 9% of calories, that's still not bad though some variety wouldn't hurt.
don't get me wrong, white rice isn't the worst thing in your diet but i think it's great to diversify with some whole grains and lots of beans (a real superfood), many of which can be had for 2$ to 3$ per 2k calories.