ipod to iphone game data transfer

Hi. I have an ipod touch and I just got an ipnone4.
I'm trying to transfer game data from ipod to iphone but when I do that on the iphone, the games start from the beginning. I thought game center would help but it doesn't. Anyone know how to transfer game data, stats, upgrades etc to iphone?
I use games like tap resort, casino and a few others.


Thanks a lot I appreciate it.