That's a very good question.
As we saw in GFIII, Michael desperately wanted Anthony to finish law school. When Kay said that Anthony had definitely dropped law school for opera, Michael said, "He throws away greatness."

What "greatness"? With all due respect to lawyers, I don't think Michael envisioned Anthony as another Clarence Darrow. And "greatness" does not inhere in being a member of a corporate law firm, or doing personal injuries, real estate or divorces. Michael probably had in mind that Anthony would fulfill his own father's wish that Michael be "Senator Corleone...Governor Corleone..." Most politicians start out as lawyers.

You can argue that Michael's wish to impose a career direction on his son against his son's will is "selfish," although Michael might argue that he was helping Anthony by preventing him from making a bad career choice by pursuing opera. (After listening to Anthony in "Cavalleria," I'd have to agree!) But I have little doubt that, had Anthony become a lawyer, Michael would have wanted him to work within the Corleone empire; or if he became a pezzanovante, to help the Corleone empire with political favors. That's selfish.