When I wrote Halo Revisited and just outright called Crackdown the Halo 3 Beta, I had no idea how wrong I was going to be. Perhaps my opinion on this is colored by never playing a Grand Theft Auto game, but after reading about and talking to former GTA players playing Crackdown, I don't think so. Let me make this clear, Crackdown is great.
Why? Because you have total freedom to do anything you want in the game, it is entirely non-linear. Apparently this can be jarring at first to some, but it was eye opening and refreshing to me. I don't think I am exaggerating to say I had a similar feeling playing Doom for the first time. Finally a new type of game! Crackdown's setup seems simple. You are a genetically engineering cop working for the Agency in Pacific City, which is controlled by a bunch of gang bosses across 3 gangs. That's almost the entire preamble. As you find the headquarters for each boss, you are shown a dossier video of that boss, which provides additional color, and a little more depth to the "story", but it's not much and you don't have to follow any pre-set path to ridding the city of crime.
The games real depth though comes from the near limitless ability you have as a player to try just about anything because of your characters skills. It dawned on me this morning though that not only does Crackdown owe an obviously huge debt to GTA and the "sandbox" genre, but nearly equally to the first Matrix film. This is really the first game I have seen which captures the feeling of awakening and increasing powers from that film, called skills in the game, which eventually make you a superhero. It might be the best solo superhero game ever made. Unlike say an existing superhero game, where you start out with nearly all powers and you expect it, in Crackdown you start out only slightly super powered and you level up mostly just by doing the stuff you want to do already. Remember the first scene in the Matrix where Trinity jumps across a huge canyon between 2 tall buildings, you will do that kind of stuff all the time in Crackdown, and you will love it. I have spent hours just running on rooftop to see how far I can jump once I leveled up my agility skill.
I should re-address the Halo 3 Beta tying. I was extremely disappointed with Microsoft when this scheme was announced, like what kind of piece of crap must Crackdown be for it to need this marketing stunt. I think Crackdown was initially harmed by this, gamers just wrote it off no matter how how good the reviews where. Look at sales past the initial surge, Crackdown for the week of April 15, 2007 according to Videogame Chartz, moved only 15,673 units in the US, for a grand total of 597,498 units. It sprinted to 495,984 between 2/25/07 and 3/11/2007, then really trailed off and now looks like it will not hit the magically million sold mark. That's a shame, because this game deserves to in your 360 right now. This interview in Eurogamer with Crackdown producer Phil Wilson is a great read and explains the marketing thing and what developer Realtime Worlds was trying to achieve.
You also might need this guide to get all the achievements.