Also Symbian had a relatively good security architecture, with its micro-kernel and the permissions model introduced in S60 v3.
Android security lags behind, because Google doesn't want to force OEMs and providers to provide updates. Additionally the OS architecture makes it pretty easy to extract an APK and reverse engineer it, even if written with the NDK.
But in any case, the best exploits are social and there isn't any help there.
Most of the users get p0wned trying to find stuff for free in dubious sites, and installing it, instead of paying for the real deal.