It's beyond me why you would put Berthier anywhere near Lannes or even on the same level of Ney and Soult. He was Napoleon's right hand; able to turn every thought of his he spit out into cohesive orders. But- once without him he crumbled.
Sure, he did have his moments of glory which one can attribute soley to him; one such example would be Arcola and Lodi, possibly even the entire Italy campaign. He achieved this either through military skill, which he then lost, or mere luck alone. Nevermind which one it was, the years of the empire were not a blessed time for him.
During said time he allowed himself mistakes of such magnitude that many a Marechal, possibly even Napoleon, didn't doubt he might be sabotaging the army on purpose.
The most prominent one of these 'mistakes' would propably be the following:
Prior to the Landshut Campaign had Napoleon dispatched Berthier with definite orders; Gather and concentrate the army at Ratisbon.
Berthier though was more inclined to follow his own, in his mint brilliant plan. Rather than doing as told, he scattered the army.
The other Marechals criticized his "suicidal measures", but as he was acting under Napoleons authority they complied. Only shortly before the Archduke attacked was Napoleon able to correct this utterly insane maneuver, and subsequently beat back the Austrians.
Napoleon himself once said (speaking of Berthier) that "[...] he was not fit to command 500 men."
"The shadow of the genius in which he walks mantles his stupidity, and, by the dim glory it casts over him, magnifies his proportions. [...] this is the secret of Berthier's fame."
Not to mention his treason. He was an, excuse the language, ass licker. He stuck with whoever was powerful, so much so that the King didn't want him anymore once Napoleon had fled from Elba. He might have claimed utter devotees to Napoleon many a time, but he still abandoned him mere days after he claimed he would fight to the death for him.
The very day Berthier proclaimed said he rode off to defend Charleville-Mezier.
After he had left, Napoleon spoke with the Duke of Basson. He said that "He will not return." The only answer he gave to the shocked disbelief that the Duke returned ("What? Would Berthier take such a farewell?") was that, again, "He will not return." The Emperor was not mistaken. Even he knew of Berthier's lesser character.
On my phone, will correct grammar and spelling later