That's an interesting explanation R5, and I like that thought process... "Like 'Band of Brothers'" makes a lot of sense...
I agree with Jman too, about a lot of it depending on how you view the EU... There are years between ANH and ESB, which is a big gap to grow a bond. Then, as MikeT just mentioned, Han's willing to throw his life down for Luke. He calls him his friend for sure (I'd totally overlooked that part of Empire), and much like Chewie on the Carbon Chamber platform, he's willing to die... The deck officers merely call him Cmdr. Skywalker, and just acknowledge he hasn't checked in... It's possible some others left in search of him but I'm going to guess only Han was willing to. That speaks volumes.
Also I think we have to look at Luke as having nothing... He's lost his home, and what family he had. He loses his best friend a short time later, after a brief reunion.
Now in the time between ANH and ESB, I think it's safe to say LUke would've made new friends... Wedge for instance. I imagine he's one of Luke's buddies. I think the bond Han, Leia, Luke, Chewie, and the droids to some extent, is a deep friendship though... Han's older than Luke, but I never really thought of their age gap as that distant. Experience, yeah, probably. Han's kind of immature in his own ways too though.
I like to think that, by ESB, Han and Luke are more than just comrades in arms, but also good friends, and that Leia is in there too. By ROTJ, they're bonded even closer since they all sacrifice their time to their cause to save Han, and Han is ultimately brought even closer in with them. I get what you were saying though R5, and that makes a lot of sense to me.