And you can't even really compare the IPC of processor architectures with different ISAs directly, its often easier to solve a problem in one ISA with less instructions than in a different ISA. RISC architectures often do less work per instruction than CISC architectures, but ARM has some features like instruction predication and argument shifting that mean that its individual instruction are often more powerful than, say, MIPS.
And it is actually fair to compare processor that have different clock rates, because often the architecture determines how fast a chip you can make. Itanium servers are only clocked at around half the speed of other architectures because the ISA is very complex and that's as fast as they can make them, and so comparing e.g. Power and Itanium processors of equal clock speed would be horribly unfair to the decisions that Power made that allow them to clock so high.
So to get a fair comparison you really want to just build the best processor of a given architecture you can on a given process, and let them fight it out like they do here. This can be pretty hard to do, since the performance of different company's processes on a given node can be rather different. I seem to recall that Intel could put maybe 20% more current through a N-gate on the 65nm node than their competitors, for instance, but using the same process would be the ideal.