For RIM to duplicate the iPhone would require them to give up on a lot of long held beliefs (e.g. physical keyboard), to ignore most of the tech pundits (the pundits themselves don't like to remind us that they were busy ridiculing the very concept of a one-button phone right up to and in some cases even after it started selling like hot-cakes), to focus on the consumer instead of the business user and last but by no means least to madly start implementing and iterating on their own consumer eco-system.
Now the iTunes store is by no means perfect, but if you don't have a drop in replacement for it, what are you going to replace that part of the eco-system with? I think a lot of people grossly underestimate the time and effort it takes to create a system like the iTunes store, and never mind even all the iterations in features... how about the task of sitting down with every single recording industry association in every country that your product will be sold? How about doing the same thing for movies and then telcos? You'd have to be a masochist of the first degree.
On that note, one of the enormously revolutionary things that Apple did was to break the choke-hold that telcos had over the handset manufacturers. On an iPhone, you always have access to the App store and iTunes stores... on a Blackberry it is up to the telco whether you get App World at all.
In any case, RIM should play to their own strengths, not Apples. RIM groks business the same way Apple groks consumers. (But of course business users are also consumers, while this 'should' give Apple a big advantage breaking into the corporate market, they consistently fail to capitalise on it. I think the difference is they have to fight for the corporate space, whereas in the consumer space everyone else is falling over themselves competing to make the cheapest (read as: least profitable, also in the sense of 'nasty'), ugliest and hardest to use devices).
RIM has their own eco-system in the corporate space, mainly revolving around the BES (Blackberry Enterprise Server)... but what does that do? It encrypts your email and pushes it to you (via Canada). But is that really such a big deal now?
They have a plethora of device models, with differentiation based on presence or absence of things like GPS, trackballs and cameras, and also how wide you want your keyboard to be. I'm not convinced that having so many options is helpful, but they seem to have a hard time deprecating the old ones.
Lately they have been making inroads with the teenage market in the UK because they have a cheap alternative to SMS (one advantage of running your own server infrastructure I guess). But I wonder how many of those teens also carry iPods?
It is easy to look at a Blackberry and say something like "oh, this is why they're failing, their camera is bad and the browser is worse". But that is overly simplistic. When comparing the iPhone to other smartphones, the iPhone has two killer features: ecosystem and ease of use. You may put out a phone that physically has all the features of an iPhone, but you get an extra 10% megapixels... and the world is not going to beat a path to your door.