iOS leads the pack but android updates aren't that fast either. Apple has a lot of pull and which is why they can roll out updates almost instantly across all networks. Meanwhile, Verizon is busy adding bloat to android updates while also not giving a damn about windows phone.
Sent from my GS4
It's not that Apple has pull, they just have very specific hardware they work with so they don't have to deal with hardware certification, and they typically don't announce anything until the updates are well into the carrier testing phase. By the time they acknowledge a release is coming, it's typically already in the carriers' hands, and being tested. This makes it SEEM like things are moving more quickly, but it's not as fast as it seems.
Google used to announce when they released the code to the wild, so it felt like it'd take forever for an update to hit since it still had to go through hardware and carrier testing. They've tweaked their stance lately and have looped in "preferred manufacturers" during their testing so the hardware testing phase goes more quickly, but we haven't really seen the fruits of that yet.
From what I've seen of MS so far, they're more Google than Apple, but there's no telling how far along testing was when they actually announced the changes in the next update. Considering Nokia was well into the development of Amber, I suspect they push code to the OEMs fairly regularly.
The biggest difference between the three is that because Apple doesn't have to deal with hardware certification, mid cycle bug fixes always make it out. Google has pushed countless security patches and bug fixes that end users never saw because of the headache involved when it comes to pushing an update to thousands of different handsets on different carriers. MS hasn't been slow it seems, they pushed the first update out within months, and by the time 8.1 rolls around (let's say 15 months from 8's initial release), they'll have pushed out 3, which isn't bad at all. Trust me, Android users have it WAY worse than we do when it comes to updates.
I will say this, Verizon is notoriously slow with updates, and they have frequently opted to skip updates because the benefit wasn't worth the effort.