Who was the most underrated player in your opinion?

Personally, I think Nezhmetdinov was the most underrated because he never got to be World Champion and helped Tal beat Botvinnik in one of the World Championship matches.

Me.

GM Motex

Nezhmetdinov is often mentioned in this type of threads, but he is fairly well known for a player with his results. He was never top 20 according to Chessmetrics, and his by far best result in a Soviet Championship was 7th.

One rather unknown player nowadays is Erich Eliskases. He won against Capablanca and Keres in Semmering/Baden 1937, won Noordwijk 1938 far ahead of Keres and Euwe and was undefeated in eight consecutive tournaments from then on, and still good enough to beat Fischer in 1960. In the 1930s he played four matches against Spielmann and Bogo, winning all four. He was Alekhine's second in the title match in 1937, and was scheduled to challenge Alekhine in 1941 but by then he had moved to South America. Here he is outplaying Capa in the endgame:

http://www.chessgames.com/perl/chessgame?gid=1004796

My list of underrated players are:

Paulsen, Chigorin, Euwe, Spassky

Wolfgang Unzicker.