Having seen only a bit part of his work, I feel that Coppola is an extremely ambiguous directer whose love for cinema went into the right, modest direction regarding his way of referencing to the directors he 
admires. However, I tend to find him a bit too "shy", too controlled and, though that may sound absurd, a bit too "un-egocentric" as well. It should be mentioned that I just watched the first two GODFATHERs within the last two weeks for the very first time (I purchased the newly "restored" box set as a Christmas gift) and was immensely impressed and consider both to be real examples of greatness, but, for a reason I don't know myself, wasn't overly enthusiastic about them. 

1. [Dementia 13] (1963) 7/10 
2. The Godfather (1971) 9/10 - 22/25 
3. The Godfather: Part II (1974) 9/10 - 23/25 
4. [The Conversation] (1974) 9/10 
5. The Godfather: Part III (1990) 9/10 
6. [Dracula] (1992) 8/10 - 21/25 
7. [Jack] (1996) 4/10 
8. [The Rainmaker] (1997) 7/10 
9. [Youth Without Youth] (2007) 8/10 * - 11/25 

* Note that this rating isn't meant to be serious and indicates the entertainment value of the film rather than its poor quality - definitely a guilty pleasure in the truest sense of the word. A, for example, didn't like it at all, unfortunately. The 11/25 is the more serious rating which displays my shock that a filmmaker like Coppola seriously unleashed an esoteric, ridiculous potboiler of that kind. 

[ ] = German dubbed version.