No, they're bad.
1) They're still on 32nm which means worse efficiency.
2) They have far fewer transistors than Intel chips. 1.2B for "8 cores". Even a Sandy Bridge E quad has more with 1.27B. A true six core Sandy Bridge E chip has 2.27B. AMD's "8 core" chips sound massive, but they don't have very many transistors. 8 core Haswell E has 2.6B transistors — twice as many as AMD's "8 core" Vishera.
There is only so much you can do with clockspeed when you're dealing with a chip that has so few transistors. However, Lynnfield quads have just 774M transistors and they're faster per core than Vishera even at a lower clockspeed! A 4 GHz Lynnfield quad will beat a 4 GHz Vishera in gaming benchmarks, and that's a 45nm chip with so few transistors:
FX 8350, 4 GHz
i5 760 quad (Lynnfield), 2.8 GHz
Cinebench R10 single thread benchmark:
FX: 4338
Intel: 4512
Dragon Age Origins 1680 x 1050, Max, no AA or Vsync
FX: 139.2
Intel: 142
Dawn of War II 1680 x 1050, Ultra
FX: 70.5
Intel: 70.8
WoW
FX: 91.5
Intel: 89
Starcraft 2
FX: 47.9
Intel: 44.9
Now, keep in mind that the Lynnfield chip has no hyperthreading, is from 2009, and is running at a 1.2 GHz slower rate. FX is competitive with a gimped quad from 2009. That says a lot.
I realize these are older games that are not heavily threaded like newer ones, but I don't have better benchmarks in front of me (using Anandtech's CPU bench). It still says a lot that single thread performance of a tiny old Lynnfield chip beats FX clocked 1.2 GHz higher, or is around the same performance. Lynnfield also has 7 MB less L2 cache.
The one thing in Anandtech's CPU bench that FX chips seem to really excel at is 7-zip. I assume this is because each of the four modules has two integer threads and one fpu.
FX: 23223
Lynnfield: 11641
Lynnfield also falls well behind when an app can take full advantage of the eight FX threads:
Cinebench R10 multithreaded
FX: 22674
Lynnfield: 15060
But, let's look at 4 core Haswell at 4 GHz... (4790K, 88W)
Cinebench R15 multithreaded
FX: 640
Haswell: 894
single-threaded
FX: 64
Haswell: 181
Bioshock Infinite SLI, minimum FPS (1080p max, 2x 770)
FX: 12.1
Haswell: 28.3
single GPU, minimum FPS
FX: 9.6
Haswell: 28.6
Battlefield 4, minimum FPS (1080p max, 2x 770)
FX: 63.6
Haswell: 82.3
If you have a water loop and can push enough voltage into an FX to get near 5 GHz then you can game at 4K relatively well because of GPU-bound scenarios. It won't be as fast as Haswell, but it's reasonably competitive with Ivy Bridge E (4930K). But, you're going to pay for the power bill.