Google is the giant of the Internet, especially on search and online advertisment. If you ask me who is the potential candidate to compete with Google? I will say, is not Yahoo!, is not Alibaba, but is Apple.
Why not Microsoft? Microsoft is another IT giant, Microsoft can compete with anyone. It will not inspire you.
Google is a service provider on the Internet, but it also an Internet media company. Apple is a hardware, a software or an entertainment related company by selling iPod and mp3 songs. How could these two companies could compete with each other?
Google is good in search, and Apple is developing its search technology as well. Apple add in spotlight technology in Mac OS X 10.4 Tiger, it is a search function, not just to help user to look for a data file on the hard disk, but it can help user access to application easily, by 'searching' it.
The different is Google search the Internet, Apple spotlight search your desktop. This is not all the truth, as you know Google Desktop application search your desktop too. Is hard to avoid competition these day.
Searching is just a start. Browser application lead me to relate Apple as the potential competitor of Google.
Google search already dominate the Internet, if it can control the software platform like Microsoft does, that will be great. Google's answer for the software platform is browser--Chrome.