Kiribati is generally the first country to celebrate New Year's Day in most years.
The reason is geographic and political rather than cultural alone. Kiribati includes the Line Islands, which use UTC+14, the world's furthest-forward standard time zone. Kiritimati, also called Christmas Island, is the best-known inhabited island in that zone.
When midnight arrives on Kiritimati, much of the world is still on the previous date. Kiribati moved the International Date Line around its eastern islands in 1995 so that the country would share the same calendar day, eliminating a large date difference between its island groups.
The exact order can be discussed differently if people mean a country's capital, its earliest territory, or the first inhabited place. That is why lists may mention Tonga or Samoa as early celebrants. For the country with territory in UTC+14, however, Kiribati is the standard answer.