The reason these taxes aren't paid is because of loopholes. Eliminate the loopholes, and you can lower the actual rates. I would favor a flat tax rate if it meant that the loopholes were eliminated. Pay a certain percent of your income -- the same percentage as everyone else, but that's on all income including capital gains (you made the money, you pay the taxes).
There is no way that you can justify a person making millions in income paying less taxes than I do (as far as actual dollar figures). The actual dollar amount they pay should be higher than the dollar amount I pay, because their income is larger than mine.