The iPhone 3G was released in 2008, if you've been using it for the past 2 years then it was 4 years old when you *started* using it...
While it's true that Apple obsolete the hardware fairly quickly, using microsoft as a counter example is ridiculous... Microsoft were pushing windows mobile 6.x when the iPhone 3g came out, the hardware this ran on is also obsolete and cannot run current windows versions, and unlike the iPhone old apps won't run at all on current versions. Windows phone 7 came out in 2010, and this os (as well as the hardware it ran on) has already been abandoned.
Apple are probably the least terrible when it comes to obsoleting the hardware.
As for trusting google, that's just as bad as trusting microsoft... But at least with android, you have the option of custom non-google rome.