Gameboy/Wonderswan replacement CPU

[ProDigit]

So, you guys might know that the gameboy had a Z80 chip, and the Japanese competitor (created by the same engineer), had a NEC V20 chip.

The Wonderswan had 5-6x longer battery life (40 hours on 1xAA, vs 30hours on 4xAA on the gameboy).

My question would be,
If I were to develop a replacement console that would run at between 8-10Mhz, what would be the best, least energy consuming chip?

The NEC V20 did an amazing job on battery life for the console, 9 years after the Gameboy was released.
Now, we're almost 20 years later. Chips have evolved.
Are there any chips of this caliber that are made on 28 or 14uM or smaller?

[Guest]

I just read up on the NEC V30, V40, and V53.
The V53 seems nice. Still looking for more modern, and especially more energy efficient.