Speaking to supporters at the first of three appearances during the evening, Obama recounted a series of episodes he said make this "a historic time."
"We just went through the worst financial crisis in our history since the Great Depression, worst financial crisis," he said. "We have an Arab Spring that is transforming an entire region of the world. The structure of the global economy, the changes in technology all are happening at a breathless pace."
He said his administration had averted depression, saved the auto industry and has seen 22 consecutive months of job growth in the private sector.
"We're starting to see manufacturing come back to the United States," he said.
Obama said he and his supporters need to "tell a story about everything that we've gotten done over the last three years so that people have confidence that change is possible," but also "tell a story about where this country needs to go."
He said the choice facing voters in November will be "a starker choice than we saw in 2008."
"In 2008, I was running against a Republican nominee who agreed that we should ban torture, agreed that we should close Guantanamo, believed in climate change, had worked on immigration reform," he said. "And so as profound as the differences were between myself and John McCain, there was some sense of convergence when it came to some very important issues.
"If you've been listening to the Republican debates, they have moved," he said to laughter from the audience. "I've stayed here. They've gone in a different direction.
"Now, that's going to make for a hugely important, hugely consequential election," the president said.
Obama echoed many of the same themes in a later appearance at the Apollo Theater in Harlem, where -- as he opened his remarks -- he noted the presence of the Rev. Al Green and sang some lines from the R&B singer's 1970s hit, "Let's Stay Together," drawing applause from the audience.
"I cannot sing like you," he told Green. "But I just wanted to show my appreciation."
Obama also spoke at a fundraiser at the home of director Spike Lee.