Quoted from SantaEatsCheese:This game is loaded to the top with toys. 4 bouncy martians, 6 little UFOs, and 1 big UFO... and every toy does something.
It's loaded, I always laugh when people say the game is empty. Don't forget it has 3 ramps (one of which diverts to a lock), a strobe light, motorized target bank, etc. 
I think the main reason is it's fun for all skill levels like some have said. Newbies get the big dumb saucer shot they can focus on, which feels awesome. Intermediate players can reasonably achieve Total Annihilation, which feels awesome. Expert players can rule the universe, which feels awesome.
