Very real, very complex, and very rewarding.
Essentially, in this turn-based game you build units at bases, attempt to capture valuable territories, and crush the enemy either through an objective or simply by destroying him. This all takes place on a hex-based map, with a good variety of differing terrain that affects mobility and defense. Though this seems simple, it is deceptively so. There many nations (USA, Russia, UK, Japan, China, Israel, to name some) and hundreds of units of every kind. Air, land, and sea power are all well represented in this game and most units have more than one weapon or attack type to engage the enemy with. A myriad of real-world weapons, with roughly equivalent strengths versus various unit types, are respresented and named within Dai Senryaku VII. M109, M1A2, Merkava 4, Challenger 2, MLRS, SMERCH, T-90, AH-64, Ka-50, MiG-29, F-22, etc... they're all here, with numerous statistics to boot. If you have no idea what any of those are, then that's probably a good sign that you'll get lost playing this game.
The graphics are best described as "spartan". The 3D map graphics are very simple, but pretty intuitive and clean looking. The battle graphics get the point across but not much else, with 2D representations of the units firing upon one another and inflicting casualties. It wraps up quickly, which is good, since there will be a lot of fighting going on in the average game of DS7. The sound is equally bare bones, and the music is pretty annoying (but it can be turned off). Artillery sounds kinda like artillery, rifles have a generic gunfire sound, etc. It's really there to just get the point across of what's happening in a battle. Much more impressive are the large number of maps the game comes with; the sheer amount of single player content could probably keep you occupied for years if you never tired of it. There's a robust map editor as well, and the game also comes with multiplayer. In the admittedly unlikely event you happen to find a friend or two who likes this stuff as much as you, this can be engrossing, as it has for me. The game really does have incredible depth and realism despite it's simple appearance.
Ultimately, I can't really give this game a high score because it's so specialized and so niche. It also definetly lacks in some areas. But the main game, the meat of the experience, contains so much that if you're into it then you'll like or even love it. if you're truly interested in the challenge of real modern military tactics, then give it a try.
ADDENDUM: Just to make this clear. If you're like me, and love serious military strategy, then this game is easily 9.0+. If you're not, then 7.7 probably being pretty generous for how you'll enjoy it.