None of them is a completely accurate translation, but given the context of the phrase you used as an example:
- In France we use the expression comme cul et chemise (which is, once litterally translated, something like as ass and shirt). Even though it contains the word cul it is not offending, just familiar. You can sometimes hear it in "G rated" TV shows.
We liked the same places, the same foods, and the same games. We were like two peas in a pod.
Would give:
On aimait les mêmes lieux, la même cuisine, et les mêmes jeux. On était comme cul et chemise.
This said, I dont like it so much.
- You can also use inséparables. It is appropriate in all situations but it is a quite less accurate translation:
On aimait les mêmes lieux, la même cuisine, et les mêmes jeux. On était inséparables.
- And you can also use être comme les deux doigts de la main (which means something like to be like two fingers of a hand):
On aimait les mêmes lieux, la même cuisine, et les mêmes jeux. On était comme les deux doigts de la main.
It is not fully accurate either: être comme les deux doigts de la main implies a strong moral commitment and suggests that each finger can absolutely stand by the other one.