No, James Cameron has had many big successes in the past, but nobody stays on top forever. He has not won any Academy Awards - or film-related awards of any kind for that matter - since Avatar in 2009. As for box office numbers, he is one of Hollywoods biggest earners, cumulatively speaking, but almost all of that took place several years ago.
Like many successful people, James Cameron used his success to coast and create many less than stellar movies. Other directors like Woody Allen and Steven Spielberg consistently make top quality and innovative movies time and time again. Regardless of their success, they are committed to the craft and respect the audience. Cameron became sidetracked by the money.
When you look at the top directors still working, James Cameron falls somewhere in the middle range. He's better with action movies than thought pieces. Expect strong characters, but not many that live on their own, as he's more concerned with plot. If you're looking for work by better rounded work, try Woody Allen, Terry Gilliam and Martin Scorcese.
James Cameron is a talented director, and I agree that he is definitely ONE of the best in Hollywood or even in the world. However, I believe that Steven Spielberg should take the honors as today's best director. His films are legendary, and everyone knows his name as he has worked with many of the biggest stars in the business.