Currently, the "best" cpu/mobo combo, in terms of the amount of performance you'd get out of video games without going overboard, would be:
CPU: i7-930
MoBo: Gigabyte x58a-ud3r or equivalent board. If you are doing extreme overclocks, you can get the higher versions of these boards (ud7, etc).
Granted, these are not the theoretical best parts that money can buy, but anything over this would be overkill for gaming alone.
Edit: see above, I type these things slowly at work.