death to capslock

Yeah, I always thought the "Sirius sees Harry as James" is either overexaggerated or misunderstood (by characters in canon). The thing about Sirius is that he's one of the few people who are actually like family to Harry--the only Wizard. (Remus could have been, but because of his personality he's withdrawn politely back to "kindly interested adult".) So Sirius' reactions to Harry are more like family--part of that is James. He's bound up with the guy, sees himself as Harry's godfather, sees him as part of James and understands him in that context. That doesn't have to mean he wants James back and is living that fantasy through Harry--he really doesn't. Commenting on a way one is different from a parent, even if it's in a childish way (since Sirius is kind of pouting there) does not mean you don't know the difference. Sirius just seems to appear to do that to people because nobody else really cares about Harry's family. Slughorn does something similar with Lily, but nobody thinks he's confusing Harry with her.