1UP writes: "Most games that involve extraterrestrials place you in the boots of a gun-toting human, slaying aliens en masse. Like its predecessors, Destroy All Humans! Big Willy Unleashed reverses the roles, letting players harness the power of alien technology and put the boots to humanity. Due to its similarity to the previous titles, though, the novelty loses its appeal far more rapidly than you might expect. I like slaughtering humans and all, but I'm starting to feel like the series needs to take a new direction rather than sticking to the safe route and just iterating on the concept.
Players might be shocked at Big Willy Unleashed's brevity -- I played through the 23 single-player missions in less than six hours. There's a decent amount of extra content present to keep you playing, though; you can play through several optional side missions if you want to upgrade your weapons, or you can completely ignore them and the game's main story, spending your time terrorizing humans in one of four open-world environments. Even after you finish the single-player campaign, the experience never really ends, as you can always return to an area to try out the upgraded weapons you've unlocked".