lost game data

I faced the same problem !

Game data and settings are part of the backup. Did you try to use the latest backup of your 3G to restore your 4S from?

I just migrated my son from a 3GS to an iPhone 4 running iOS 5.01. I wiped the iPhone 4, reactivated it, then restored from a complete backup of his 3GS.

His Harry Potter Lego saved game setttings were not preserved. He was, understandably, disappointed.

I haven't evaluated his other games. In general iOS 5 migrations have been difficult, with more than expected work to reinstall apps, delete crashing apps and resume them, and restore accounts.