He was basically a glorified bodyguard. At the end of GFII, we saw Neri pushing past Rocco and making moves on Tom to replace him as Michael's #2 man, perhaps even consigliere. But in III, Michael's "legit" (or thinks of himself as "legit"). BJ's his lawyer (not consigliere--Michael always was his own consigliere, even before he went "legit"). Vincent shortly pushed his way in to become Michael's alter-ego and successor. Neri wound up kissing Vincent's hand.