The reason his film career didnt last longer
Stallone: Renny Harlin, Richard Donner, Rob Cohen, James Mangold, Ted Kotcheff, John Landis, Robert Rodriguez, George P. Cosmatos, John Huston, Norman Jewison
Schwarzenegger: John Milius, James Cameron (3 times), John McTiernan, Walter Hill, Ivan Reitman (3 times), Paul Verhoeven, Chuck Russell, Peter Hyams, Andrew Davis.
Van Damme: John Woo, Roland Emmerich, Peter Hyams & John G. Avildsen (DTV movie).
Schwarzenegger was able to work with better directors which lead to better movies. While Stallone directed a lot of his hit movies he also worked with quality directors. Van Damme got stuck working with these Chinese and Hong Kong directors and his movies suffered. Now he might be still doing DTV movies now because even Stallone and Schwarzenegger cant open a movie anymore not called The Expendables. I don't know if it was the drug issue that stopped better people from working with him. But even Seagal was able to get Exit Wounds after his career had tanked.