Plus keep in mind that Apple is DOWN 4.38% YTD.
http://finance.yahoo.com/echarts?s=%5EIXIC+Interactive#symbo...
Average is positive.
Microsoft up a bit more than the average.
Apple down incredibly more than the average.
Steve leaving probably helped a couple percent, but it's just noise.
The facts you cited aren't my facts; stocks and bonds are indexed to a benchmark made up of their peers. Matching the index is expected, beating it is great and underperforming it is really bad. For Apple and Microsoft, their peers are in the NASDAQ index so that is the benchmark by which they are judged.
Microsoft being up 37% in contrast to its benchmark being up 28% is not "a bit more than the average". It is beating its benchmark by 32% which is an incredibly good performance. Likewise, Apple underperformed its benchmark horrifically.
Think about it this way - $100 invested that returns 37% compounded growth over 8 years is now $1,240.98. However, $100 invested that returns 28% compounded growth over 8 years is now $720.58. Hopefully you can see why your downplaying of Microsoft's accomplishment seems a little silly. Oh, and the same $100 invested in Apple over 8 years would now be $69.88.
They are about the same, all showing mean reversion.