most dominant chess players (for entire life dominance)

some chess player are strong but  unfortunately not so long like fisher,morphy 

in my question i seeking for player who dominated his era like   40 or 50 year dominance on chess maybe not the best but still in top 20

i read ivanchuck is one of them even he did not get the crown ,yet he make a dominant chess in his entire life some players becaming dull in late of his lifes,karpov is ok but he is not strong as before

now the question is  WHO IS THE TRUE LEGEND ,who stand against the time !

Clearly Lasker.

morpyh..no he retired the game early his chess career is about 20 years or so , he is not even close , read the question it is not that i am seeking the best chess player the question is about who can stand against the time

Lasker or Alekhine.

Lasker was WCH from 1894-1921 (28 yrs) and still a world-class player at least up until the Moscow Tnmt of 1935. Without WW 1 Lasker would've lost his title to Capablanca after 1914 and before 1921.

Steinitz was unofficial WCH 1866-1886 and the first official WCH 1886-1894 (28 yrs total)

Alekhine was WCH from 1927-1935 and 1937-1946 (17 yrs total) when he died in office. Without WW2 I'm sure he would have lost his title before 1946, most likely to Botvinnik

Botvinnik was WCH from 1948-1963 with 2 1-yr "interuptions" by Smyslov (1957-8) and Tal (1960-1) but he was a world class GM from the mid 1930s to 1970.

Here's a link with a (now somewhat outdated) list of the Top 100 GMs of all time for a 20 yr peak. 

http://www.chessmetrics.com/cm/CM2/PeakList.asp?Params=199510SSSSSWS000000000000111000000000000010100

thank you , very helpful link

Kasparov too