But assuming you want a PC or laptop for home use then as fo3nix says, the Intel Core 2 Duo are the "best" at the moment.
Here is a list of the current Intel CPUs, both for desktop and laptop
http://www.intel.com/cd/products/services/emea /eng/319641.htm
So the "best" desktop CPU is the E8500 (but note the CPU alone costs over �175)
The "best" laptop CPU is the T9500
If you do plan to buy a PC or laptop you can look at that list above and work out how powerful it is (the list has the faster CPUs at the top of the list)
Intel are gradually dropping the Pentium name and although there are some dual core Pentium CPUS they are not as good as the Core 2 Duo.