GGG is a nice little movie that keeps you entertained throughout. Michael Winnick manages to keep the cadence really steady, so if you like the first ten minutes you'll probably like the whole thing. This is actually a great accomplishment as too many movies starting with a similar vibe get goofy and boring after a while.
Plot- and character-wise Winnick uses many stereotypes, the ingredients of GGG are very familiar. But the overall result looks fresh and new, so there's nothing wrong with that.
The hypocritical prejudices against the use of stereotypes are a main source of GGG's humor. If you can't laugh about people with prejudices complaining about the different prejudices of others, you should skip this movie.
The two movies GGG really reminds me of are "Lucky Number Slevin" and "Snatch". Both have a rating of 8. That sounds a bit high for "a nice little movie", but GGG's current rating is 3.7 and that's just embarrassing. So 8 it is.