VirgilCaine said:
First of all, the D20 system isn't what you want for realism. It came from D&D and D&D was made to be fun first, not realistic. My opinion, at least. For realism, you might try GURPS.
"Realistic" is a matter of degrees, and can be adjusted. Look at "Blood and Guts" --- depending on how which optional rules you decide to use, you can probably go anywhere from G.I. Joe to "Blackhawk Down" in terms of realism. "V for Victory" in Polyhedron was another attempt to offer a more realistic look at war.
I would note that one of the creators of d20 Modern was a tank commander in Desert Storm. I'm sure he was trying for "fun over realism"...but he's probably the only game designer [only one I'm aware of, anyway] qualified to speak as to what "real" is really like, based on first-hand experience.
Yeah, the default setting for d20 Modern is "action movie," but a few tweaks and some research can make it feel more real.
Whether Blood and Guts or V for Victory are really "realistic" or just the sort of things that seem realistic to folks who have never experienced actual military combat are two different issues....
verisimilitude \ver-uh-suh-MIL-uh-tood; -tyood\, noun:
1. The appearance of truth; the quality of seeming to be true.
2. Something that has the appearance of being true or real.