I'm personally switching to an Intel chip, but that's mostly because there are no AM3+ Mini-ITX boards. Both AMD and Intel have high performing CPUs, an FX-8350 should get you well above 60 fps in everything provided your video card is capable of matching the performance.
Passmark scored your old CPU 2,000 and the FX-8350 9,000, so about a 450% increase in power.
I don't expect there'll be that big of a difference in games with all the other hardware taken into account, but it'll still be a massive increase.