Crackdown is great fun, but if you're a completionist, I'd suggest getting some Orbs maps before you start grabbing anything you find. I didn't think anything of it first time I played through, and ended up with 499/500 agility orbs, and the sound the orbs make when you're nearby haunted me for weeks afterwards.
Prototype is another great game with plenty to keep you busy, and although it does have Crackdown-orb-y stuff, it's a lot easier to get hold of a map after you've already picked some up, and be able to check off the ones you've already got as you go through.
And in all honesty, Fable II is another amazing game, but I felt it was fairly short, and it's not as fun to run around killing people after you've finished that than it is to run around killing people on Crackdown or Prototype. I even found myself having fun running around having fist fights with pedestrians, infected, and military alike on Prototype.
I think of those three, my personal opinion would be to go with Prototype.
Oh, and yeah, if you liked Lost Odyssey, as Beatrix said, give Blue Dragon a go. Mistwalker are doing a damn good job so far if you ask me.