There are actually bigger pricing differences than you imply among the various cloud services. Many of these have to do with the size of the compute or storage that they supply: if your needs differ from the standard package sizes from the major services, it pays to shop around and match things up accordingly.
However, in general I would agree that they have to do a better job of differentiation based on non-pricing things. AWS and Azure and Google Compute seem to be the leaders in terms of other value-added services. The rest have not done a great job showing what else they offer, or hide their offerings with fine print or gobs of pages that you have to wade through to figure out what they really have. With some cloud providers, you have to become a customer before you actually can understand what services they offer.
Not to pick on them particularly, but take a look at GoGrid -- they have dozens of services and products (not really sure which is which), and under each one are pricing details that would make a lawyer proud. Trying to get a grip on why they are better than AWS is daunting. And even trying to get pricing details requires assembling a dozen different details.