Well, in 1/30th K&C dids two series of USMC/Japanese for about the Iwo Jima time period (late 1944-45). Very nice figures but didn't sell all that well so they were limited (and therefore a bit hard to get)
Figarti has doe some nice Marines, and as mentioned above, they have different time periods represented.
I plastic, the TSSD Marines and Japanese are quite good. The can be converted to all kinds of other figures. If you follow some of my plastic conversion threads you can see that I was inspired by the Pelilieu scenes to convert a running mortar crew.
The Old Marx Marines really aren't that bad. Also in plastic there were "US Marines" (actually closer to Army) and Japanese from Airfix.
Over the years there have been a number of unpainted metal figure kits issued.
The BEST USMC figures right now are in 1/35th scale, both resin and plastic kits. Dragon Models (DML) currently makes the only "Guadalcanal vintage" Marines.
So, Marines are out there, just limited by the money you want to spend, or your ability to assemble figures.
Gary B.