With today's rally, the S&P 500 is now up 150% since its closing low on 3/9/09. Relative to other bull markets going back to the late 1920s, the current bull ranks as the fifth strongest of all time.
As shown in the table, the strongest bull market for the S&P 500 was a gain of 582.1% from December 1987 through March 2000. In order for the current bull run to move into fourth place, the S&P 500 would need to rise above 1743.4 without a 20% decline on a closing basis. Based on current levels, that translates to a gain of 3.1% from here.