In the article they meant no dominant film among the nominees.
The sentence that closed with the phrase "... and this year has no dominant film." is copied below. I guess one could take the sentence either way, as referring to domination in theatres, or domination in Oscar nominations. I think the domination in theatres interpretation is clearly the most sensible one. "Big-box office films" refers to performance in theatres, not the number of Oscar nominations garnered by a film.
But big-box office films tend to juice the ratings -- the Oscars (news - web sites) haven't approached the 55 million who watched when "Titanic" won in 1998 ... and this year has no dominant film.
Seems like the author is hinting to compare "Titanic's" box office performance with the box office performance of Mel Gibson's "The Passion of the Christ." The theory seems to be that unless a film's box office take beats or approaches Titanic's, then Oscar viewership won't "be juiced" as a result. I think a simpler theory is that Oscar viewership is maximized when the bigger box office films are represented with nominations for awards. People like their favorite film(s) to be recognized. Maybe the decline in Oscar viewership is a simple reflection that Hollywood in general, and the Oscars in particular, are not in harmony with audience sentiment.