Worst CPU I can think of was just about any P4, be it skt 478 or 775. Some of the Pentium D's were stinkers for the price. However the Pentium D 805 was cheap and one of the earliest dual cores (maybe the first, I can't remember). The Athlon 3800 was way better though and ended up about the same price.
Best CPU's..in context because of price and what else was out at the time, including cpu's from the same 'range' that were not as good value, i'd go with
E6300 Core 2 Duo
Q6600 Core 2 Quad
AMD Llano range because of the value of the IGP.
Core i7 920
Core i7 2500
Some of the Bulldozers ended up pretty good value for gaming.
I had an Intel 486 that was poor value at the time...can't remember the spec, something like sx25.
What? Again with the poor memory of P4, I'll repost what I said earlier :
"Ugh. P4 was the fastest thing out during the Northwood era, and also had low-cost variants that could overclock up to the fastest retail chips out there.
People with memory problems seem to judge P4 for some rough spots :
Socket 423 / Willamette, waste.
RDRAM, overpriced.
Prescott, hot and slower IPC.
Cedar Mill, way too late to be competitive.
That ignores a long period of time from the 1.6A to the 3.4C of Northwoods kicking butt. The 845 and 865 DDR chipsets also had great stability, overclocking, and AGP/HDD/USB performance.
One can certainly say that they never should have gone down that road to begin with, and I'd agree with that. Tualatin was pretty good, and I'm sure if they put more resources into the development of those successors things would have been better. Even so, it's plain ignorant to say that P4 overall was anywhere near worthy of being mentioned as 'worst ever', particularly when there was a pretty good run of being as fast or faster than anything on the market."
I refurb PCs for a local charity food bank resale shop, and we get non-profit editions of Windows 7 to put on them. P4 HT models with 2GB of ram actually run Windows 7 fine, which is impressive. Of cource so do the A64 models. But P4 Northwood predated P4, and it was rock solid stuff. P4 had a crap beginning, and a crap ending, but the middle period was actually outstanding for the time.
http://www.anandtech.com/show/1117/16
You'll notice the P4 was well over the AXP by the time P4C arrived, and even P4B was easy to clock to 3ghz+ previous to that. I loved my AXPs, particularly my mobile 1700+, but to say that P4 sucked is extremely ignorant as a blanket statement.