Godfather Part II is amazing cinema, and you should watch it!!

Part III (where that line comes from) is not nearly as good of a movie, but perhaps worth watching for the completionism; it's got its moments. It's also got some stiff acting, difficult-to-follow storytelling, and confusing editing. Michael mellows and becomes much warmer as an older man; it's kind of like Flynn from Tron to Tron Legacy, except the Godfather movies are orders of magnitude better.