Best Graphic Card



PCI-E 2.0 will run any cards fine. PCI-E 2.0 or PCI-E 3.0 will give you nearly identical performance and in some tests
PCI-E 2.0 is faster than PCI-E 3.0 - both when compared x8 and x16 (oddly).

I´d always recommend using the latest PCI-E revision whenever possible, but it doesn´t mean that PCI-E 2.0 isn´t useful.