They are both legendary producers with a lot of amazing movies to their credit.While Spielberg is more prolific,Cameron is more of quality over quantity.That is why two of his movies :Titanic and Avatar are the two highest grossing movies of all time.He also has movies like Terminator and Aliens to his credit.Spielberg on the other hand has produced blockbusters of his own some of which are:Jaws,Jurassic park,Transformers and Indiana jones film series.
Therefore i throw this question to movie enthusiasts. Who do you think is better?

They are both pretty good at what they do, but the Canadian Cameron is actually a real life genius which technically makes him smarter than Jewish American Spielberg.

Steven spielberg hands down. james cameron might be a genuis when it comes to scifi but berg has tried his hands on so many types of movies from scifi to biography drama to comedy etc and still pull it. cameron makes movies almost once in every decade.