You mean 'good' as in 'tastes good', or as in 'nutritious'? The nutritious part would make sense, but might possibly lower the tastes good part (e.g. school lunches over here are nutritious but seldom tasty).
In fact, it would be insane to serve food with poor nutritional value, since that would negate most of the physical training.
You are chatting with a man that must surely be in the top 0.01 percentile, in terms of his accomplishments in taking maximum advantage of the mess hall. I prided myself on my ability to get many times more food from that facility, than I (or any other service member) rated to receive. I was the undisputed hero of the shop where I worked (ATC facility), and they always sent me --sometimes with an assistant or two, to help carry all the food-- on the chow run. My strategy and techniques for exploiting that place, were legendary.
I'd even bring back enough food for all the married guys (who didn't have meal cards) to regularly eat good lunches/dinners at work, so they didn't ever need to bring food with them. Plus, I prepared each 'to-go' box totally PACKED with a great variety of food, well organized. Often more than a couple dozen boxes, in total (EACH MEAL, the chowhall served)... all from a resource of only a few (5 to 8) meal cards, per visit.
My fridge was always packed with meals like veal parmesan and pasta, chicken breast w/ rice, a good ham & cheese omlet, etc. -- with all the sides of veggies, fresh fruit, desserts, and so on. Food was one thing I took very seriously. Why? Because I was 238 lbs of solid, lean muscle, and you need good food to build a body like that. (And thus the reason I can't get that big now... because no one is cooking for me)
ANYWAY... the reason I was such a massive over-achiever in this department, was not because the food "was just okay". I'm very picky when it comes to food. So bearing that in mind, and taking into account my massive exploitation of the chowhall facility, you can put 2 and 2 together and conclude that the food was pretty good. It 'built my body right', and yeah, I wolfed it down every 3-4 hours or so, and loved it.
It was good, seriously. It's really the best thing I have to say, about my Marine Corps experience. And btw, the food in boot camp... oh man, it was fantastic - probably the best of my whole service. This may seem counter-intuitive. But, you've got to remember this isn't prison - where they're just trying to keep you alive. No, here, they're training you... and working you hard. And as a valuable asset to the U.S. gov't Defense Dept., they have a strong interest in making sure you are healthy & strong. Thus, they feed you well.
It is possible to get a visitor's pass, and go visit a military base. You can indeed go into the mess halls, pay of course, and check out the food. So, you don't have to take my word for it.
Now, having said all this - is it "fine dining"? Not exactly. But whatever, it was good food. This idea that the just serve a bunch of slop in the military, is totally wrong.
And the best part is... getting more...

...enter, my patented 'Dessert Fox' tactics.