The iPhone has seen success from day one and has continued success through all of it's phone and OS updates. It's been chugging along since 2007, like you said, with regular hardware and software update intervals. The style of the phone and the OS are more or less the same since day one. 3.5 inch screen, round home button with a square icon, silver edges, buttons, speakers and plugs in the same place. The OS is a app tray with the OSx style dock.
New features are added and the user interface is streamlined. People know what to expect, and this is what keeps most of them coming back. They don't have to learn something new every year.
Android started on the opposite end of the spectrum. While the Android OS is relatively uniform, hardware and custom overlays/roms have created a hodgepodge of a product that has always been behind iOS in terms of usability and uniformity and always behind in terms of hardware and apps.
But there are a couple things that people tend to overlook when they compare the two OS. One is that iOS had a good headstart on Android. The first Android device was released over a year after the iPhone, and while the HTC Dream sold semi-well at the start, Android lagged far behind iOS, and even Windows Mobile. Despite a rocky start, Android converged with iOS and Blackberry sometime at the end of 2010. During 2011, we've seen soaring growth, to where there's something like 500k+ 'activations' daily. The news reports are saying that Google is getting ready to announce 1 million daily in the next few months.
In November, Android is going to hit an apex, a point where it really begins to shine. And where I believe it will begin to outpace iOS at an alarming rate. We'll see a few things happen next month that will change Androids standing, at least in my mind, in the smartphone world.
1. Android will finally catch up to the iPhone hardware.
The iPhone has always been a step ahead, which is something that I don't understand. An example: iPhone 4 was released in June of 2010 with a 'Retina' display. 326 ppi. Android still has never had a phone over 220 or so ppi. The Galaxy S2 was really the first phone to outpace the iPhone 4, a year and a half later, and it still doesn't have a high ppi/resolution screen. The screen is a full inch larger, which is very nice, but Apple still holds the title as the highest clarity screen. And the A4 processor has given most of the Android phones a run for their money. Again, the Galaxy S2 easily outpaced it with the dual-core cpu, but a month later, the iPhone 4S was released with the A5 with the killer PowerVR SGX543MP2 GPU. It pretty much smokes the Galaxy S2 in terms of video processing power.
Next month will be the first time Android has a screen that compares, surpasses even, the iPhone. Galaxy Nexus will have the same ppi as the iPhone, and it will be a full inch larger. The SuperAmoled also smashes the iPhone contrast by a factor of over 100 to 1 (100,000:1 vs 800:1). The RAZR will be quick to follow with the same 720p display. We all are a little disappointed that the Galaxy Nexus will still lag behind the iPhone 4S in terms of GPU, but the PowerVR SGX540 is nothing to scoff at, especially at the 300mhz clock speed.
The point is: Android will dominate the the hardware side of things from here on out. I don't see Apple changing their form factor by much. They may increase screen size to around 4", but Android will retain the largest screen. And Apple has nowhere to go in terms of ppi/resolution. They've already claimed to have hit the limits of the human eye. And they'll need to play cath-up in terms of contrast. The iPhone 5 and it's quad core A5 may take the title CPU for a few months next summer, but Android will quickly regain the lead. The quad core Tergra 'Kal El' will be out relatively soon, and we'll always see Android phones with CPU/GPU from the different companies, which gives it a good advantage.
2. Android 4.0 is huge.
Last tuesday, I was talking to my friend (an Apple enthusiast) about Ice Cream Sandwich. I knew about the new App switcher, and as a prior WebOS owner, it's something that I've really, really missed in Android, and iOS. I didn't count on it having the 'flick-to-close' app and notification features, though. I didn't really expect to see much change at all to the rest of the OS. As it turns out, I was very wrong. I'm waaaaay more excited for Android 4.0 now after watching the live stream on Wednesday. Google really exceeded my expectations.
Adapt, Adopt and Improve. Google has been doing this from the start, and they've done it in 4.0 in a huge way. They've listened to what people say about their product and have really done something about it. Ease of use is not something that Android has been known for, but they specifically addressed that in their presentation. This stigma is something that will be difficult to change for Android, but they have taken a huge step in the right direction. People will notice and will appreciate these changes. Segmentation has always been a big problem as well, but it looks like Google is taking efforts to quell that problem as well. I hope they can, but it really depends on the network providers. And it won't effect me, because I'll root and update to the latest build anyway.
On the other spectrum, iOS has kept steady. It's been user friendly, it's been stable, and it's been the same. iPhone owners enjoy and expect it. But it's starting to become a problem. Example: it took 2 years for Apple to adapt the notifications tray. Example 2: without rooting your phone, you are locked into using the default keypad (and a lot of other default options) that is just terrible, compared to some of the text prediction keypads out there. This isn't a big problem for people that jailbreak, but there are millions of iPhone users out there that don't want to 'void their warranty'. I don't want to dog on iOS too much, as I'm pretty biased against it, but iOS 6 is going to need some pretty big improvements to match Ice Cream Sandwich. iOS isn't the tog dog anymore. The playing field has been leveled. This is a good thing because I still feel that the mobile OS platform has a lot of growing to do, especially when it comes to the tablet form factor. Desktop OS's have really been stagnant for a while now, and it's really refreshing to see the mobile OS's advance so rapidly.
Anyway, this is getting a bit long, so I should wrap it up.
Android is growing in a major way. If you look at graphs of current mobile data usage, you'll see that Android is sky rocketing there, just like their market share. iOS is starting to loose it's advantage there as well. The Android App pool is swelling up just a fast. We'll see Android pass Apple up in every category in 2012, or at least match it. The only title Apple will hang onto is the iPad and the tablet market, but there is a lot of room in that market and it's growing rapidly. So are Android tablets.
I'll probably get an iPhone 5, and I don't doubt that it will be a great phone, but I've got at least 6 months to get to enjoy my Ice Cream Sandwich

The Android experience maybe a little different for me than most, because I plan on staying on top of the latest hardware and software, trading up when a good replacement comes along, but I think that others will find ICS just as pleasing, even if they stick to the same phone for a year or so.