When I first heard about Crackdown and it's included Halo 3 Beta invite...I figured the game probably sucks and this is just a stunt for sales. Well, I was wrong. Crackdown is an awesome open world game.
I was having a blast just running around and looking for power up orbs around the city. Your characters physically gets bigger as you advance and you really mold into a super hero.
Their LOD system is pretty incredible... you can see for a mile. Not to mention, you can shoot a rocket launcher for a LONG way and still see the end explosion.