Symbian was quite good, the only thing was the strange Symbian C++ dialect, which wasn't something sorted out by iPhone until the store finally came to be.
Symbian the OS was solid. Symbian the devices were mediocre. iPhone was much more polished and consumer friendly. Touch screen, size, weight, iOS, the browser, data -- it's hard to attributes iPhone's success to a single thing, but the overall package was head and shoulder above anything else.