I can't count 10 sandbox games, but both Prototype games, Darksiders 1 and 2 if 2 comes through the way I think it will, AC Revelations and Batman Arkham City. That's about 6 games. I would've counted the original Hulk: Ultimate Destruction and Crash Bandicoot: Mind Over Mutant, but both of those are from the last generation.
Prototype Prototype 2. Saints Row 1 SR2 SR3 RDR GTA4 Just Cause Just Cause 2 The Saboteur Crackdown Crackdown 2
The Assassin's Creed titles probably should be in there, but I tend not to include them, for reasons unknown. Other titles (off the top of my head) that have sandbox elements-- Burnout: Paradise, Brutal Legend, Arkham City.
Take the high road- give out all of your free damns right now. When you have no damns left to give, you'll be a happier person. --SquallWindblade