Losing a BEST friend of 7+ years. WTF? Any advice is great!

I'll keep this as brief as I can, but it won't be easy:

I've had a friend who's been my "main man" since the end of college (about 7 years now). In the beginning, he sort of "forced" the friendship (called me a lot, IM'ed me, etc) until we started hanging out more.

Long story short, we became best friends. We hung out quite a bit. Gave each other rides to parties. Hooked each other up with girls. Drove to pick up the other if one was too drunk to drive after a party. We even defended each other in a fight when we were accosted by some racists in a bar. Our sense of humor is the same, and our timing was impeccable. We played off each other perfectly and could get people laughing like we were paid to do it. It got to the point where if one of us showed up to a party alone, people would ask where the other was. Everything was great.

Great, that is, until about 2 years ago. I started law school and he got a girlfriend. He also got pretty tight with another mutual friend of ours. We all hung out together still, but I noticed a severe drop off in calls and invites (granted, I was busy with school, but I tried to make the best of it). My time was much more valuable now due to my studies, and I tried to set up appointments to hang out, but he would cancel at the last minute and flippantly offer a change to some other day (which I couldn't do, since I had school work), leaving me high and dry the one day I could hang out.

Its gotten progressively worse. He spends all his time with his "new" friend (our mutual buddy) and girlfriend now. I offer a night to hang out and there's always "something" going on. Now its at the point where I can leave numerous messages on his voicemail (no, not like a stalker. More along the lines of a message a week on three different weeks) and he just doesn't call back. E-mails that used to be responded to quickly and in detail are late and two sentences long. Since we share friends in common, we'll occasionally hang out with "the guys" (birthdays, mainly), and when we do, we're right on the money again. Perfect timing, great fun. Unfortunately, the next day, its right back to "ignore" mode.

Here's the deal: I don't want to lose a friendship, especially one that was so strong, for nothing. We didn't have a falling out, we never really fought, and (I thought) we would always be friends thanks to the solid foundation we established over the years. What the hell?

I sent him an e-mail a few months ago explaining how I felt, and how I didn't want ours to become a "bullshit" surface friendship. I wasn't accusing or angry, I just wanted him to know that I felt we were boys and that it didn't seem right to be put on the back burner for no reason. His reply was, an I quote, "I don't know what to say, other than, your right". That was the entire message. I was expecting that some of his behavior would change after that, but it didn't.

Here's the question:

I don't want to lose this friendship. I have other friends, but none who I am that tight with. I've seen him "write off" other people in the past, and I'm starting to see that behavior toward me. Should I just not care? It seems like my few attempts to have a real talk with him are met with indifference. Should I just pretend like none of it matters and maybe one day we'll start to hang again? Or should I just write him off completely?

...sorry for the long post!