What do you consider as "best"? Many people will look at it different from Intel to AMD based on their "fanboy" level or what they considered to be best.
Benchmark wise, the new Intel i7 980X will be the best chip out, next month. You'll have others that say either the AMD Phenom II X4 955 or Intel i5 750 are the best chips out, since they provide the best bang for your buck performance wise in gaming. You'll have others saying the new AM3 6-core Processor is the best.
There is no clear answer to what is "best" beside what is "best" for your needs and budget and that will vary from build to build.
On the desktop, the best you can get is the Core i7 980X. The Xeon 5600 series 6-cores are coming soon for servers, but there's always crazy server chips out there from Sun and IBM that have a gazillion cores or whatever that blow desktop chips out of the water.
If this is a theoretical question, then that's you're answer. If you're speccing a new system then what do you want to do with it and we can advise the best processor FOR YOU.
In my honest opinion the best processor is the one that does everything you need it to while being fast enough for your needs. The best processor depends on the needs of the person using it. There is no sense having a Core i7 for checking email only.
If you mean by sheer performance then the answer is simply the six core i7 980 X and of course it costs $1,000. Of course you also need an X58 board and triple channel memory kit to go with it. Now if that's a bit out of your price range then you need to specify what you are willing to spend and what you plan to do with it.
which is chip and best processor now a days?
I suggest kettle fried 4004s in peanut oil, the 10 Micrometre process is surprisingly resilient to heat and its ceramic packaging just seals the flavour in while providing that extra crunch us chip and best processor enthusiasts long for now a days!