A lot of different people, from many different walks of life, from different places the world over seem to really like what James Cameron does. That doesn't mean everyone likes it. But the kind of people that like his movies are diverse -- young, old, rich, poor, white, black, dude, chick. I can't think of anyone who's movie's have had shuch broad appeal since Spielberg's early days.
Personally, I think there's value in that.
Again the idea that financial success is an indicator for quality.
In my opinion the term "mass appeal" shows already a really uncritical attitude towards products of the culture industry, as it suggests that the success of Hollywood movies is somehow democratically legitimated, and that's imho not true.
It's also not true that those kinds of films are the only films people want to see, it's also the other way round; culture not only mirrors but also shapes society.
"The standardised forms, it is claimed, were originally derived from the needs of the consumers: that is why they are accepted with so little resistance. In reality, a cycle of manipulation and retroactive need is unifying the system ever more tightly"
Looking at culture as a means to make profit is something I find highly questionable, as it naturally loses its autonomous and educational quality.
That doesn't mean that such films are of no value, mind you, but they're not more than consumer goods.