Of course Bush has the power to do that, he could commute the sentences of (or pardon outright)
In general, the controversial pardons by Democrats appear to be different than the ones by Republicans. Bush Sr. pardoned folks involved in the Iran-Contra scandal, Bush Jr. pardons (well, commuted the sentence) someone in his administration involved in outing CIA agents, Ford pardons Nixon. Clinton, on the other hand, pardons rich folks who gave money to Democrats, and Carter pardoned Vietnam vets. Of recent presidents, only Reagan appears to not have had too controversial of pardons.
What's the difference between the Democrats and the Republicans? The Republicans all pardoned folks working for the Executive branch. That just seems like plain corruption to me. Republicans can get away with breaking laws when a Republican is president. There's no accountability. So the president (or vice-president) can have folks do shady deals, and the people doing them don't have to worry about being caught because they know they can get pardoned.
There's always going to be controversy over pardons, I'm not arguing the Democrats have only pardoned angels. I'm just saying that Republican presidents pardon people in the Executive branch, and that smacks of corruption to the core.
Not that I needed the Libby decision to show me that W is corrupt.