All aristocracy starts somewhere, many of the great families started as soldiers or counsellors many generations back and of course provided most of the military and civil leaders of any country. Starting a new aristocracy is only restarting the process, the descendants will be a mixed bunch, some more successful than others. I don't think it is 'denigrating' Napoleon to point this out.
To use one example: Macdonald can reasonably be considered to have earned his title as well as any but his son never got beyond the rank of deputy and chamberlain to Napoleon III, he lost the family fortune and had to sell the estate. The grandson was a poet who went into the army and got very poor reports: when he requested to leave the army to try for a rich marriage the response was 'good riddance!"
How many of the sons of the Napoleonic nobility did distinguish themselves?