I just thought of this after posting in the fundraising thread. Here's a list of the wealthiest US presidents ("which the authors admit is predicated on some big assumptions and gaps in the record "), if you inflation-adjust their fortunes to 2010 dollars:
http://economix.blogs.nytimes.com/2010/05/24/net-worth-of-u-s-presidents/#But as it says, one probably shouldn't count JFK as #1, since he never had a chance to inherit that $1 billion fortune. So let's say the real top two are Washington at $525 million and Jefferson at $212 million.
Romney's fortune is somewhere between $190 and $250 million:
http://www.msnbc.msn.com/id/44125985/ns/politics-decision_2012/t/romneys-wealth-high-million/#.TpoQec0vrVVSo he'd potentially be the richest president since at least Jefferson, if not Washington.
I'm not posting this to suggest it's a good or bad thing. Just thought it was interesting.