The marines are an expeditionary force in readiness. At any given time, the Marine Corps has the capability to land up to a reinforced batallion of steely-eyed killers anywhere in the world, with air support, within 48 hours. There is no service in this country who can match that, and to my knowledge none in the civilized world who can beat it. The Marine Corps provides this great nation with a literal "911" force to call when the need is most dire and urgent.
And that's not even all. The Marines have proven to be superior at all forms of irregular, modern warfare when compared to other forces in the past decade. It is our nature to be flexible. The ability to adapt rapidly to whatever the circumstances may be and thus succeed where a larger force would bog down, is the core of our warfighing competencies.
We are fast, strong, agile, self-sufficient and above all, effective where more conventional forces are not. I haven't even touched on the most important part...our ethos. Even if other services began to gain the same compentencies, this alone would set us apart.
In conclusion, OP is a silly man.
Semper Fi from a real Marine.
-Le Jerk