From this MSNBC article on guilty pleasure movies (quote is from page 3):
Mention “Titanic” to educated, cultured folk and there’s a good chance you’ll be met with condescending sniffs and, if you’re lucky, a defiant declaration that they’ve never seen it, accompanied by a proud refusal to even brook the notion. To which I say: Shut up. What they miss is that the drippy love story isn’t what the film is about at all. It’s merely the mechanism though which we see the film’s true subject — the boat. The reason Rose is in first class and Jack is from steerage isn’t to show that love conquers all, it’s to provide an all-access pass to every section of the ship as it steams towards its doom. Chaining Jack below decks after the iceberg may smack of melodrama, but it also keeps him and Rose at water level almost the entire time and prevents them from abandoning ship before the precise moment when it becomes completely submerged. The result is that we're right there with the ship every second of the way as it slowly, inch by inch, goes to its death. James Cameron's earlier films occasionally slipped into techno-porn. This was his love song to a giant slab of steel. -Marc Hirsh
He makes a very convincing argument. The things I like about Titanic all have Cameron techno-porn at their roots.