Lee, the outgoing president, could not run for re-election, as it is prohibited by Korea's constitution. He will leave office next year dogged by low approval ratings, an impasse with North Korea, and corruption scandals involving his family and inner circle. The Korean presidency has not enjoyed a sterling reputation.
Park and Moon also bring baggage from the past.
Park is the daughter of former President Park Chung-hee, whose legacy left the Korean public divided. Some claim he was a dictator who ignored human rights and cracked down on dissent, while others credit him with bringing economic development to South Korea. Her father's assassination in 1979 ended his 16 years of rule.
Moon is a former human rights activist who was imprisoned in the 1970s for protesting Park's father's regime. He is also a former special forces commando and holds a black belt in judo. Like Park, he carries divisive associations with the past. He was chief of staff for the late President Roh Moo-hyun, who was in office from 2003 to 2008. Roh committed suicide in 2009 amid an investigation into a bribery scandal.
Throughout the campaign, Moon portrayed himself as the down-to-earth choice, calling for welfare reform and economic democracy. Both candidates pledged reforms including engagement with North Korea, reining in the country's big conglomerates -- like Samsung and Hyundai -- support for small and medium-sized businesses and more social spending, although their proposed methods differ.
"I'm concerned about homeland security, foreign policy and the economy," voter Lee Dong-hoon said. "Among those, the economy is the most important. We need to raise the number of the middle class."
The election comes at a time of sluggish growth and increasing poverty. In October, the Bank of Korea, the nation's central bank, lowered its growth forecast for next year to 2.4% from its previous prediction of 3%.
Since 2006, the number of residents living in relative poverty has jumped 10%. Almost one-fifth of the population earns less than half the national average income, according to Statistics Korea, a government agency.
Nowhere in the country is the gap between rich and poor more stark than Guryong village, part of the exclusive Gangnam district of Seoul, made famous by the viral "Gangnam Style" song by rapper PSY.
Lee Ha-soong, 80, has lived in the neighborhood for 30 years. Her home is a patchwork of wood and corrugated iron, sandwiched between other improvised cabins. In heavy rain or snow, she is forced to stay with neighbors as her 5-square-meter home floods.
After seeing presidents come and go, Lee is unimpressed by their promises.
"Every election and every Christmas, politicians come and ask me, 'How are you, Grandma? How can we help?' It's always the same questions. I tell them, 'If you can't change anything, why are you asking such useless questions?' "
Despite plans to raze the shacks and build low-income apartments for these residents, Lee is unconvinced that change will happen.
Less than a kilometer away from her shack, high-rise apartments stretch into the sky. The cheapest apartment in these buildings cost a cool $1.2 million in an area known as the Beverly Hills of Seoul.