noun which may take the genitive case particle 'no', noun
most popular; number one in popularity
Used for the top-ranked item in a popularity contest, menu, or ranking. Often appears in phrases like 人気ナンバーワンのメニュー.
この店の人気ナンバーワンはラーメンです。
The most popular item at this shop is ramen.
人気ナンバーワンの曲を教えてください。
Please tell me the most popular song.
Similar meaning, but 一番人気 is a more standard Japanese phrase, while 人気ナンバーワン has a slightly more casual, trendy feel.
Compound of 人気 (popularity) and ナンバーワン (number one), a straightforward loanword combination.