RIM has failed to attract consumers in significant numbers largely to their lack of innovation. Before you even get to the problems with available apps, versus iOS and Android, they are still pretty much selling hardware that looks like what the competition shipped two years ago.
And sure, not everyone is buying a top of the line device, iPhone 4S or Gala y Nexus etc. But the mid to low end is even more crowded: along with value priced Android and the older iPhone models, you have all of the new Windows Phones, including several decent offerings from Nokia. These don't compete yet in the iPhone 4S arena, they're not yet designed for gaming like the Apple devices and some better Androids, but they seem to be more advanced than anything from RIM.
Though I think both lines, RIM and Win7Phone, are lagging the others for a simple reason: they're still thinking in 2005 business phone language, even as they pursue consumers. These guys thought the hardware didn't matter back then, and they were eaten alive because of it. As a consumer, you may only buy an iPhone 4 or 3GS today, but you know there's a top of the line model if you want one. But Nokia's top of line only goes halfway to the top, while RIM seems to get off at the second floor. Every phone does email. If that's all you're building for today, you should fail at it.