Isn't the current Intel Core line an evolution of the Pentium M (2003), itself an evolution of the Pentium III (1999)? Apple starting a fresh design with up to date constraints may have given them room for improvements I guess.
Sandy Bridge was the last really big architectural change. It seems heavily inspired by the Alpha EV8 design (Intel bought Alpha from HP in the 2001) with of course, a very different decoder section (they wrap the x86 decoder around a RISC architecture).
