Investment guru Jeremy Siegel still favors stocks as the best long-term investment for the next handful of years despite chances of a flat 2019.

"There are challenges that we face now," including rising interest rates, the midterm elections and U.S.-China trade tensions, the Wharton School finance professor told CNBC.

"I'm looking flattish" for the coming year, he added.

However, Siegel said he still favors stocks long term, adding it will be the best performing asset for investors looking out three to four years from now.

"The selloff in emerging markets has presented unbelievable value," Siegel said.

To be sure, the S&P 500 and Dow Jones Industrial Average dropped in volatile trading on Monday as a boost from news in China and Italy faded and losses in energy and financial stocks weighed, but gains in technology stocks helped limit losses and lifted the Nasdaq.

“Investors are looking for opportunities to buy right now. They are taking advantage of the recent sell-off to buy high-growth stocks,” Jeff Carbone, managing partner for Cornerstone Wealth, in Charlotte, North Carolina, told Reuters.

While profits of S&P 500 companies are expected to have jumped nearly 22 percent in the third quarter, according to Refinitiv data, the outlook for future growth due to concerns over trade, rising costs and other factors.