A 10-block stretch of Wilshire Boulevard in the Koreatown neighborhood of Los Angeles suddenly has become a hot spot for bank-stock investors.

Nestled among a four-story driving range and a massive modern housing complex are the headquarters of three of the top bank-stock performers this year. Wilshire Bancorp Inc. and Hanmi Financial Corp. shares have surged more than 70%, while BBCN Bancorp is up 35%.

Wilshire...