I never understood this preoccupation with OS versions, especially since the upgrade concept doesn't really parallel between iOS and Android, and Apple doesn't fully update older devices anyway. They're also starting from totally different base capabilities.
For example, almost any Android phone will be able to add in a deep Siri-like voice assistant, whereas Apple has made sure that only their latest phone has it.
Any Android phone has multitasking, whereas the first couple of years of iOS devices are not allowed by Apple to "upgrade" to that.
Ditto for folders, notifications and other things Android has no need to update for.
Android updates after 2.1 are not that significant, unless you count extra built-in support for Flash, for which of course iOS has none.
The more useful and important Android updates are with individual apps such as Google Maps, Navigation, YouTube etc... which unfortunately require an OS update on Apple devices... and iOS does not have anywhere near the latest versions of those apps.