Certainly, it's true that the Romney's made more than the Obama's or the Biden's. Even so, the disparity perhaps points up one of the key differences between Republicans and Democrats. Could it be that when one depends on Big Government to "take care" of people, one feels less personal responsibility to give oneself? As as been reported (and even conceded by liberals like The New York Times' Nicholas Kristof), liberals do indeed tend to be less generous with their own money that their counterparts on the other side of the aisle.
The contrast is revealing. In one model, the giving is voluntary. In the other, government extracts money via the IRS, and "spreads the wealth around" as politicians deem fit.