With a personal fortune valued at between $190 and $250 million, Mitt Romney would have been among the richest presidents in history, easily outpacing Teddy Roosevelt. But his wealth is less impressive next to that of Ross Perot and Steve Forbes. Perot was worth over $3 billion when he ran for president in 1992 and 1996, while Forbes' fortune topped $450 million when he ran in 1996 and 2000.
A side note: Though it might have appeared to the untrained eye that Donald Trump was, for a time, running for president last election cycle, he never officially declared himself a candidate before he decided to bow out. However, if The Donald had gotten into the race, his wealth of at least $2.7 billion (he says the number is higher) would have made him a contender for the title of wealthiest presidential candidate ever.