Samsung released the Droid Charge on Verizon in August, the S2 line (not on Verizon) in the US in September, the Samsung Stratosphere in September, and now the Galaxy Nexus in December, which is not an S2. And wasn't everybody angry at Samsung for not updating the Fascinate fast enough to Froyo? And didn't that phone have all sorts of problems (with GPS, for example) that weren't fixed for months?
HTC took months to deliver a GB update to the TBolt. Clearly not putting out phones as frequently does nothing to make updates come faster.
Apple has power in the market that the other OEMs simply do not have to deliver only a single great phone every year - which also tend to have problems, by the way, such as the iPhone 4 antenna issue, and the current battery drain issue with iOS 5. Apple doesn't have to compete with other manufacturers making iOS devices, while Motorola, HTC, Samsung, etc. do have to compete with other Android phone manufacturers. However, clearly Apple does a better job of delivering OS updates to their phones than any of the Android OEMs do (and that includes Google with the Nexus line.) Also, by the way, there remains on the iPhone an annoying bug with smart playlist updating in the Music app that prevents the playlists from updating on the device. This bug dates from iOS 3.x, and remains on iOS 5.0.1. Apple is also not perfect, and that's with only a single reference design per year.