Of those films, only two show as a sole credit to Cameron: The Abyss and Strange Days. Since the others are shared credits, in one case with about five other people, it's hard to know how much Cameron was involved - for instance he may only have story-boarded. The Abyss is a classic case of the point I was making: several parts of it give the feeling of having been written at the bottom of a treacle well (to paraphrase Martin Gardner), to the extent that it jars against the better bits. It's a long time since I saw Strange Days, but it's generally considered one of the weaker films he has been associated with. He needs to co-write, because his tendency towards cliche and bathos need curbing.
And yes, the script of Titanic is embarrassingly bad - more cliches crammed together than normal mortals thought possible.
M