They're fundamentally narrative media: a landing page proceeds serially from top to bottom. What you see first matters most; like every good story, it also needs to give you a reason to proceed down the page.
It's great when they converge — where the visual design, structure of the page and the copy itself all come together in a beautiful statement of the brand's values and the product's value propositions. But none of that can happen without a story that resonates powerfully with the people who it should matter to. On a cursory examination of landing pages, it's easy to forget that they're speaking directly to a specific group, and miss the real magic simply because you aren't in that group.