This game is hillarious, imaginative and, well, you can make cows dance!!! Its no less deserving of a 10/10.
The story is for Destroy All Humans is straight out of a sci-fi movie set in the 50s. You are Cryptosporidium 137 or one of his clones. You will use telekinesis, advanced alien weaponry, and a Death-Ray-equipped flying saucer. Without saying too much about the plot, let's just say your actions will not be unnoticed and you will have the police, military, and the secret service on you.
The graphics are just plain gorgeous. In the levels when it is day time, you will see sun reflect off the cars. The explosions are the most detailed you will see for a while. The models of the cows you can tip are perfect. Everything down to the police badges on cops are beautiful. However, there is two bad things about the graphics. As you may or may not know, this is a GTA clone. That includes the GTA like graphical problems. Occasionally objects pop in the environment and the people's arms are always moving but the hands and fingers seem immobile. However the graphics are well detailed and are some of the best the PS2 has to offer.
Compared to GTA (I'm sorry to keep bringing this up) this game kills not only in the script writing, but in the variety of voice actors. There are also sound effects. Everything from honking horns, to shotguns being fired, to your jet pack carrying you through the air just fit. Nothing in the audio department feels out of place. To me, audio perfection.
The control style isn't the most original but it works pretty well. For movement it uses the "FPS-style" movement. It works very well. Cycling through weapons, all of your psychic abilities, and flying via jet pack or flying saucer all feel simple and easy. There is also a large amount of variety in the missions. I would give you and example of variety but I would completely spoil the plot for you. There are several different mission types so the missions will rarely bore you. If they do, you can always go on a GTA style rampage, find drones (a.k.a. hidden packages), or do side missions which range from checkpoint races to more organized rampages. Nothing wrong at all here.
The story is fairly short but there is also a lot of other stuff to do. Completing everything 100% will take about 100 hours without cheats, maps or anything else. Then you can go back and retry some missions with fun twists (I bet you can't beat the Televisions of Doom mission without your jet pack and yes it is possible.) This will last a long time.
In conclusion, this game is an instant classic that belongs in any game library. I give it a 10/10 and my highest recommendation.