Apple > Google > Microsoft
Apple is Apple, Google wants to be like Apple, while Microsoft wants to be like Google.
Apple has its own style and way of doing things - they seldom follow, though they are not exempted from it ie iOS Notification Centre and iPad Mini but predominantly they are known to set the tempo while others come in, follow and improve.
Since Larry visited Jobs and heeded the advice of getting Google to focus on core products. That was exactly what he did by killing many many products and focusing on integrating and optimising the ecosystem within existing and new products to come. The ethos of simplifying the user experience with stock Android, Chrome, and even to the Apple-esque ads hints at the influence of Apple. Internally, Google is probably the largest Apple customer with their fleets of Macs.
Improving their web offerings, launching the Surface series, and attempting to unify a tablet and phone os is very similar to what Google has done in the last few years - you could say they are following Google's footsteps.
This hierarchy would also be reflective of their earnings - being in the centre, I think Google is fairly safe but with Apple and Microsoft especially with the fight between Windows 8 and Mac OS X or Surface Pro vs Macbook Air 11" - I wonder who will succeed.