A simplistic view of Flag Officer Ranks in the USMC.

Ultimate Ratio Reg and CDR Salamander are banging hard on the number of Admirals in the Navy.  I'm sure URR will come back (he said he would) and take a serious look at the number of Generals in the Marine Corps.

I want to beat him to it.

My simplistic view of the appropriate number goes like this.

2 four star Generals.  The Commandant and Assistant Commandant.
4 three star Generals.  They would be in charge of each of the Marine Corps Divisions.
4 two star Generals.  They would take care of Marine Expeditionary Brigades and serve as Asst Division Commanders.
20 one star Generals.  They would fill out all joint billets.  If the number of joint billets is greater than this number (and it most assuredly is) then it would be filled with a Colonel that is given a temporary promotion to the flag rank until his assignment is over.
Colonels and below would be as currently assigned with the exception that billets that are deemed more appropriate to the rank of Major will go to that rank and by this method we will also reduce the number of Colonels.

This is just off the top of my head but I was tweaked by URR and Sal on this issue.