As says on the topic. That's right, ol' Boney isn't around, died crossing that bridge at Arcole or had a 'whiff of grapeshot' for himself maybe, but everyone else is. That means the French still have Davout, Massena, Lannes, etc and likewise, the Allies still have Wellington, Kutozov, etc. Without Boney, would the revolution collapse under an Allied onslaught or might it be someone else's fingers on that crown? Maybe a more moderate outcome, a general who was able to hold off the Allies but know when to make lasting peace?
One thing is for sure. To say that Napoleon's marshals either wouldn't make an appearance or would otherwise shirk to some quiet corner in history would belie their fiery personalities. Napoleon's marshals were men after his own heart, talented ambitious individuals who took advantage of the collapse of the ancien regime to propel themselves to the very top. Moreover, chances were overwhelming that it would be an army man who takes control of the country. The French revolutionary civilian government was on the brink of collapse, buckling under corruption and ineffectiveness and threatened by outside invasion. That Napoleon took power was largely due to him being the most popular army commander at the time.
One thing that makes it hard to evaluate the marshals though, is the level of involvement Napoleon had in his campaigns. Most of his marshals couldn't function well without him because they simply weren't used to not having him around. Yet the clues were there, that without Napoleon this would've still been a remarkable period.