How to choose a low power Microcontroller?
TI's MSP430 is well known for its low-power: I've used the MSP430F1101 in an application which included the microcontroller, a voltage regulator and a reset circuit, which, with the controller active, consumed less than 5\$\mu\$A typical.  

It depends on your needs. My controller didn't need high speed, so I could operate it on a 32.768kHz crystal, which saves a lot of power compared to for instance 4MHz. You say you have an update rate of 3200Hz, then a 32.768kHz crystal may be too slow; you can only execute 10 instruction per sample.
The MSP430F1101A is specified at 160\$\mu\$A at 1MHz and 2.2V. This current is almost linear with frequency, so at 100kHz you'd have about 16\$\mu\$A. That's 48\$\mu\$W at 3V. Then it will run for 250 days on a single CR2430 coin cell rated at 290mAh. That's even without using powerdown modes. If you can put the microcontroller in the 0.7\$\mu\$A standby mode most of the time you can extend this easily to several years.
If you would need an opamp with that, there's the LPV521, which needs a miserly 0.4\$\mu\$A. Also discussed here.  

Be careful with the Cortex-M0 figures on the ARM website. 52\$\mu\$W/MHz and lower is indeed spectacular, but that's just the core, a complete controller needs more. The LPC1102, for instance, consumes 2mA at 12MHz and 3.3V, that's 550\$\mu\$W/MHz. Ten times the ARM figure, and almost twice what the MSP430 needs.
The Wolverine doesn't seem to be a real product yet.  

Edit 1:

3\$\times\$3200 bytes/s is a lot for a standalone low-power application. You'll fill a 64Mb Flash in less than 15 minutes. If your data is 16-bit, less than 7 minutes. And what are you going to do next? I presume you have no connection with a PC to collect the data, otherwise you probably wouldn't need that very low power. But if you're finished in 15 minutes low power is a silly requirement, let alone that the Flash needs a lot more than the microcontroller.

Edit 2:

Aha, wireless! That's new. This may be much more of an issue than the microcontroller. We've seen that &lt; 1mA is achievable, but a RF transceiver will often require 100 to 150mW when active. Try to find a solution for this. You'll have to switch off the transceiver for most of the time, but it may need some time to become active again. Even at a 1% duty cycle it will consume much more than the microcontroller. Do you have specs for the transceiver yet?