The Marines wore a 2-piece cotton Herringbone Twill (HBT) uniform throughout WWII. The first pattern was the M-1941 uniform. It included a blouse with three open pockets, two on the skirt and one on the chest with the EGA stencilled on it (as in the pic above). The trousers are simple straight leg trousers with slash pockets on the hips and two rear pockets, one with a button closure, the other open. This uniform would remain the standard through 1945, even though other options did come in throughout the war.
In 1942, the first camouflage uniform was adopted. It was reversible with the green pattern on one side and the sand on the other. This only had two pockets like the regular green one. However, pockets were on both sides (for a total of 4 pockets). This uniform also introduced the camouflage helmet cover. The first pattern helmet cover did NOT have foliage slits in it.
There was a second camouflage uniform adopted in 1942 for Raiders and Paramarines, but these are extremely rare and regular Marines wouldn't have been issued them. (I can go into further detail once I get back to my library)
The M-1944 uniforms were adopted in October 1944 and took some of the good points of the Army HBT uniform. The trousers had two cargo pockets mounted on the hips instead of slash pockets. A third pocket was across the entire rear (secured by three buttons). The new blouse had two map pockets, one on each side of the chest. One smaller pocket (secured by a single button) was mounted on the left breast and had an EGA stencilled on it. An interesting feature of these and the M-44 Camo trousers was reinforced holes in the waistband that the 782-gear combat suspenders could hook through. This allowed the combat suspenders to be worn as regular suspenders when on garrison duty.
The M-44 Camouflage uniform was very similar to the green M-44 uniform. I'm not sure the exact differences between them right now, since I'm on vacation and can't look it up! M-44 uniforms were the primary ones used by the Marines in Korea.
Web gear and equipment was different for the Marines as well. Musette bags, canteen covers, haversacks and combat suspenders were all of a different pattern from the Army and are rather difficult to find nowadays.
Hope this helps, and don't hesitate to email me if you've got further questions.