There are 100 or more "right" answers to this question as you will see. Go with what the OEM suggested. Most likely a dexos 5w-30. There are a lot of good marketing schemes and gimmicks to pull money out of your wallet for the feel good effect.
If your pockets are on fire from all the money burning to get out, then spend it on royal purple or amsoil. If you are more realistic and frugal, then a good name brand will do. If you are done paying for a label, then a good off brand will do. If it says dexos approved, then it meets GM criteria and your motor will be fine.
It's not so much the upfront, super awesome gotta-have it quality, that makes all the difference. Frequency of changing with a good filter will give you more bang for the buck in the long run.
There is tons of reading about oil on here, just search for it. Best-o-luck!