AMD Athlon II X4 640 Quad Core Processor any good for a decent gaming PC?

Its pretty old though.. Why not just get a Phenom if you're doing so?

Or a Bulldozer?

It's far better than what I have, and I have virtually no issues with gaming. Just some stutter on rather CPU intense games like Planet Side 2 or Guild Wars 2. It handles Skyrim and such with no problem, though.

go phenom

my Intel Core 2 Duo E8400 is better by 15 percent

not bad ,but the lack of l3 cache is a big drawback.
Phenom all the way.

its not bad but ya still dont beat my dedicated servers :P

Meh, go with Phenom II or the Sandy Bridge Pentiums.

Get an Intel processor.

I had the X4 620 some years ago.
You can play nearly anything with it, but not at the maximum settings.

Compared to other CPU's it sucks.
I'd recommend you to get a Phenom X4 960t, with a bit of luck and a decend mainboard you can unlock the cpu to a phenom x6.

But if you want to buy new parts all the way, buy an Intel i3 3220.
It even beats the FX 8Cores in some games, except maybe the new Vishera ones, and costs like 100€.

Currently i'm running an i7 3930k and i am fully happy with it, if you can afford it, get at i5 3550, and if you are willing to overclock it, a 3570k/3770k processor.

The problem is, all AMD processors kind of suck.
They might do ALMOST comparable to the Intel Sandy/Ivy bridge processors in games, but everything else they lag quite far behind in. It's absolutely worth the money to get an i5 Sandy Bridge over any of the AMDs, especially the i5 2500k.
http://www.hardcoreware.net/amd-vs-intel-bulldozer-vs-sandy-bridge/7/

NO!

My Phenom II X4 955 is slow for gaming. Athlon is TOO slow.

any Intel i5 over 2nd generation is good for gaming but the processor is not the most important thing for gaming the video card is for the gaming...and for a good gaming gard go for nvidia GTX 590,580,650ti or over