I like using the analogy of potential energy to think about this 'battlefield'. Each of the big 5 (or 6 if you include Samsung) has a large amount of potential energy they may be able to use over time to grow, entrnech, and profit. In the case of Apple, Google, MS and Samsung the PE is primarily profit.
In the case of Facebook, it is primsrily the social graph. For Amazon, the potential energy seems to be scale & efficiency.
I, personally, believe profit, and the ability to continue to generate profit is a better form of potential energy because it is more controllable.