I don't think that they're friendship was all fake, but as we only hear the very biased comments of Sirius and Remus reminiscing about the past, it is safe to assume that the truth lies somewhere in the middle.

I agree. I wasn't saying that I think that their friendship was fake (if that's what you were thinking), but that it wasn't one that would easily last under harsh times.

I thought that Sirius chose Peter because he was too scared to do it himself. He might have truly believed that Peter was the best choice, but I don't think he would have done that if he wasn't afraid (whether he realized it or not). Afraid that he might die or afraid that he might betray James or something else.