SourceNote: I've included a breakdown of my ideas at the bottom of the article. Skip to here if you have a low IQ/attention span.
If you're looking to invest in a new computer or a new motherboard/CPU combo and you're wondering the best way to ensure the most "bang for your buck" in terms of all round computing, here is the answer. The most bottom right processor indicates the most powerful processor for the best value, however the AMD Phenom II range is not necessarily bleeding edge in terms of pure performance. Obviously one must consider along with the processor savings over, say, an Intel Core i7 processor, the savings on the supporting motherboard and RAM. On a Phenom II you use a relatively cheap AM3 based motherboard, and you have the option of running the cheaper DDR2 RAM as opposed to the expensive DDR3 that is compulsary for both Core i5 and Core i7 CPUs. In addition to this, the AM3 platform is likely to have an extended life by comparison to Intel's LGA1156 or 1366 sockets. I have the feeling that Intel will drop one, if not both of these platforms before AMD cuts the life support on AM3.
Keeping the same CPU socket is important if you're one of those people who likes to upgrade their machine fairly frequently. The cost of a new motherboard along with a new CPU may be too expensive. In addition to this, the platform may also be suited for those who wish to keep an older machine running. Say your Phenom II dies within a few years, you could possibly replace it with AMD's next high end CPU. By that time of course, this one could be obselete, but that isn't important if you just want to keep an older machine running at the same or slightly higher operating capacity. And again, we come back to the issue of the supporting parts. I feel that LGA1156 and LGA1366 motherboards will still be quite pricey, even in 2011. The case is probably not going to be the same for AM3 boards. Intel can afford to hike prices for their newest products for a relatively long time period, because there are so many computer enthusiasts who are willing to pay a premium for their top tier components.
One thing that I have noticed about Intel vs. AMD myself is that in terms of general computing and multitasking, Intel seems to have the upper hand. I am not a biased person, owning both Intel and AMD based computers. At my school we have computers in our study centre with mostly the same specs, but some use a Pentium dual core and some use an AMD Athlon X2, both at roughly the same unit of GHz. Both processors are also built on a 65nm process. However, the Pentium machines are noticeably faster running Windows XP.
What would my advice be? Well, if you want a ridiculously cheap dual core desktop for general use, I say you should invest in a present day single core AMD Sempron and unlock the second core. This is the cheapest method of getting a dual core processor. If you're looking for a high end gaming machine, then you should aim for an LGA1366 Core i7 machine. If you still want some power for gaming without ridiculous pricing then you might consider getting hold of a budget Pentium processor such as an LGA775 model, specifically E5200 or E5400, and overclocking it to 4GHz or so with the aid of a sufficient cooling fan. The stock fan simply will not do for overclocking, in any case, so look up your options for your socket platform and CPU if you plan to overclock more than a few hundred MHz. This solution is still just fine for gaming if you would rather pump more funding towards an amazing GPU - this is more important than the CPU in gaming, really.
If you're interested in running a HTPC (home theatre pc), even for full HD video, then pretty much any Athlon X2 or Pentium dual core upwards will work. For an HTPC you want a processor that is fairly quick and powerful but also runs quite cool so you don't need a big noisey fan to cool it and ruin your movie experience. (Also note that most HTPC cases have built in cooling solutions so the industrial strength fan idea goes out the window!) I recently read an article on amazon UK where a reviewer said he bought a 2.6GHz Pentium E5300 and managed to overclock it at an acceptable temperature to 3GHz in an HTPC. This speed is more than sufficient for full HD video, assuming that you have a decent graphics solution too. (Can anyone say "dedicated video card"?)
My recommendations for CPUs at different computing levels:
Basic use/office work - AMD Sempron unlocked to dual core/overclocked or, if you're feeling snazzy, Athlon X2 energy efficient.
Good value general use/gaming - Athlon X2 or Pentium dual core (e.g. E5400) overclocked (there is also a Phenom II X2 which can potentially be unlocked to quad core) coupled with mid range/high end GPU.
Video encoding - High end dual core e.g. Phenom II X2 or preferably a quad core Phenom II X4/Socket LGA1366 Core i7 coupled with mid range/high end GPU.
High end gaming/bleeding edge/Crysis/bragging etc. - Socket LGA1366 Core i7 coupled with ultra high end GPU(s).