And how, exactly, is that determined if there are not hundreds of dragged-out political witch hunts to, you know, find out "if laws were broken"?
It is the job of LEO to enforce the laws. Obviously this can be done in such a way as to be unfair, and any Obama investigation/prosecution of Bush personnel would probably be exactly that. Especially since what the left wingnuts consider crimes are primarily policy disagreements.
However, your position seems to be that Bush staffers should NOT be punished if they broke the law. This is not a tenable position. In theory, at least, government officials are not above the law.
I seriously doubt that Obama or any other president is really going to pursue such investigations. It is far too obvious that he could be setting himself up for the same in 4 or 8 years. Kings generally object on principle to attacks on kings.