IMHO, Hollywood is a popularity contest. The world has many talented actors. The most successful are simply the ones people like the most. Most of the leading actors play themselves in every role, but people want to see them. Thinking of Clint Eastwood and Keanu Reeves as examples... They have a certain quality that's hard to describe. Many other actors can check off the right boxes in looks and talent but never reach their level of success.
'A Soldier's Story' was the first film I saw Denzel Washington in. It was a great movie, and all the actors were talented. One could argue the others were more talented than Denzel. But he had that special quality that's hard to describe.
With that said, I didn't like that he rushed over to Will Smith, instead of Chris Rock, but I don't have to agree with everything someone does or says. Speaking of Will Smith, the rumors about his behind-the-scenes personality have been around since he played the 'Fresh Prince of Bel Air.' Then, after he hit Rock, Smith's career took a hit. Smith had a quality that people liked - until they stopped liking him.
If by ‘the greatest actor’ you mean the most popular - then I must recuse myself. I rarely agree with the popular consensus about anything. The fact of Jackson Pollock garbage selling for $200 million comes to mind.
For the most part, popular consensus and independent thought are mutually exclusive phenomena.
As for Will Smith, I never much cared for his schtick - before or after his fall from grace.