It's the first three Rambo flicks delivered in chronological order (except possibly without First Blood), told through a mixture of in game cut scenes and, more predominately and amusingly, direct footage from the films. At one point, for instance, you'll be asked to take down a helicopter with an explosive-tipped arrow. Should you aim correctly, you're treated not to a spectacular, 3D-rendered explosion taking place in the game engine, but an abrupt transition to the exact footage of the helicopter in question exploding partway through First Blood Part Two, or whatever the second movie was called.
Somewhat unsurprisingly, the game, like all three sequels, pretty much immediately ignores the is "war is bad" message of First Blood in favor of, promoting, you know, the exact opposite. In Rambo, war is freaking awesome.
If you wanted to be intensely boring, you could describe Rambo as a 3D, on-rails shooter using an automatic machine gun. I prefer to describe the game as sort of like Crisis Zone, without the cover mechanic because cover is for sissies.
As mentioned earlier, the game has one goal: make you feel like the most stereotypical, hardcore, mass-murderin' badass action hero in history. In this respect, it is successful to the point of hilarity. Armed with a machine gun with a ludicrously large magazine, you've got effectively no reason whatsoever to fire off little bursts to take off individual enemies, like you might in a less well-endowed game: you're meant to spray the screen with that M60 (or whatever it is) that you're holding.
Enemies appear onscreen, complete with (in a legitimately clever design move) a small circular meter above their heads that changes from white to red as they get closer and closer to firing upon you. This little timer does two things: firstly, it gives you an extra strategic edge in prioritizing targets, and secondly, it gives you a ridiculous amount of time to fire at your idiotic enemies before you yourself are fired upon. Baddies appear by the dozens at any given time, and they'll often jump onto screen and just stand there, waiting to fire. They demand to be taken out. They don't exist to serve as a challenge, or to test your reflexes: they are there only to be killed by your inaccurate flood of machine gun bullets.
And if that weren't enough, Rambo also has a "rage" meter that fills with every successive kill. If you fill the rage meter, four things happen for a limited amount of time:
1. You get unlimited ammo.
2. Your bullets have a bigger impact radius and do more damage.
3. You become invulnerable.
4. You are treated to a sound effect of Rambo screaming "ARRRRRRRRHHHHHHHH" at the top of his lungs.
The end result of these bonuses is that once you hit the "rage" button at the front of the light gun, you become the personification of death itself. If you were allowed to be a bit careless before the rage bonus, you're allowed to basically act like an idiot once you become an invulnerable, screaming psychopath with limitless deadly bullets. Literally dozens of bad guys will fall in a matter of seconds as you spray back and forth, back and forth, watching soldier after soldier fall without ever removing your finger from the trigger or pausing even a second to aim with any degree of accuracy. As I said before the jump, it is absolutely impossible not to activate a rage bonus and subsequently feel as if your dick has suddenly and violently grown an extra six inches. Your mind will reel at the sheer stupidity and classlessness of what you are doing. Best shooter ever with genuine movie clips throughout the game!