They're both crowd pleasers that use cheap trickery to get you emotionally involved, the first a kid and a woman, the second a completely fairytale romance. Add to it sweeping, dramatic music, uncharacteristic length (for hollywood films) used to full effect, intense "action" and you've got the "epic" feel of Cameron's films.
I like his films but he's not showing much desire to do anything else, which is kinda disappointing.
Aliens is a perfect example. A great movie - but far from the artistry of the original.
Ridley Scott can also be accused of following the crowd pleasing formula with Gladiator (which I think is rubbish), but at least he has two artistic masterpieces to fall back on (Alien, Blade Runner).