Equal processors
Core 2 Duo = Phenom 2 X2 series, Athlon 2 X2 series (Phenom 2 features larger on die cache compared to the Athlon 2 series. All of the Phenom series are actually Quad cores, with only 2 cores that actually work. It is a popular practice for people to buy Phenom 2 X2's and unlock the remaining 2 disabled cores, turning it into a quad core CPU)
Core 2 Quad = Phenom 2 X4, Athlon 2 X4
Core i3, i5, i7 = Phenom 2 X4 (Black Editions) clocked above 3ghz are the only real contenders against the Core i5 and i7 series. The Core i3's don't hold a candle to any of the Phenom 2 X4 series.