I think the top, regarding security, profit, energy consumption and size, would be the google data centers. You just can't fight Google when it comes to that.
I guess it depend on a lot of factors such as energy efficiency, secure and a lot of other stuffs. Most of the search engine corporations such as Google have world class data centers however as far as I know Google's data centers are not much energy efficient.
are the four I know of. I haven't really had need of using any other ones apart from Google, but I have seen others using them. and I know they're relatively large.
Those seem to be search engines? Not necesserily data centres..
They are huge datacenters and also have several linked together as well.
But the majority don't actually run their own data centres in the above list; for example LINX are present in Telehouse, Equinix, Interxion and Telecity RedBus facilities.
This is where European peering and US peering differs a fair amount, as we generally have mutual exchanges not tied in with a particular facility.