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 < 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?
The instruction time is 1/25M = 40ns. Assuming that your interrupt routine is around 20 instructions (it's probably less from the sounds of it), then the routine will last 0.8us.
Assume that the active mode current is drawn for 6us after the ISR has finished, at which point it instantly changes to 2.1uA (for simplification).
In 1ms, the routine will be firing for 6.8us (in active mode) and LPM3 will be on for 993.2us.
If the values you quoted are accurate, then assuming your micro has a 3V supply, 99.32% of the time it will consume 3 x 2.1u = 6.3uW.
For the rest of the time (0.68%), it will consume around 25 x 195u x 3 = 14.6mW.
Since you have the power consumption and the relative times, you can work out the average power.
Best Answer
Could be a number of reasons : is the crystal oscillator working? I don't see your program setting port 2 up to enable it.
Here is an example "Blinky" program whose current consumption has been measured under 1 uA (with no LED!). A more complex version implementing a 1970's style LED digital watch runs on the 2553, again under 1 uA (display off!) in under a kilobyte.
It's not in C but I think it's pretty easy to read, and you may find settings you need in the Init_Clock or Start_Delay procedures.
It uses a package "Timer_X" to handle the low level details of setting the oscillator and timer : the package spec is
and the package body (implementation) is