that link only explores some games performing on pcie 2.0 and pcie 3.0. pcie 3.0 just started to appear on motherboards. most game developers won't take advantage of that bandwidth for quite some time. if you're looking for gaming performance improvement, wait for new consoles to come out or new pc games - that properly utilize pcie 3.0.
right now, pcie 3.0 would show the most improvement on sandy bridge xeon servers. another area is gpu computing where apps can use extra bandwidth. for gaming, it's not necessary...yet. that could change in 1-2 years from now. pcie 3.0 does have tangible advantage over pcie 2.0. it'll take some time for software devs to make use of pcie 3.0.