Whether Symbian is a good platform or not involves more than just if the code is functional. Sometimes a lack of applications is driven by a more fundamental weakness in a platform. One of the reasons the iPhone and iPad have done so well courting application developers is that Apple tries to keep everyone marching in formation, moving the platform forward without leaving current customers too far behind. (Their formation, of course, but they are Apple)
A good example is the "pixel doubing" that went into the early iPad design. That intentionally structured the design of the platform so that applications written for lower resolutions would continue working against the higher pixel counts. That's the sort of subtle thing you do to keep developers happy and application development flourishing.
Faced with the same sort of devices with multiple resolutions problem, Android leaves the whole mess in the lap of application developers. And Nokia has just abandoned the old stuff. If you're a phone developer, how would you feel about that? A lot of things like that influence whether applications are built for a platform or not.
And, yes, Microsoft has bullied their way into a winning position using their operating system monopoly for a long time, with IE being a good example of that. I don't think it's safe to assume that tactic will keep working anymore though. I don't know anyone who feels Windows compatibility is an important thing on their phone or tablet today. At best, I might want something that opens Word or Powerpoint documents someone sends me in an e-mail. You don't need Microsoft for that on your phone though. Their software is only needed if you expect to edit the documents with low risk of corruption, and that still happens on desktops.