It is only the death of the original Xbox Live, but it still feels significant. The games will still be there, you can still get your Halo/Halo2 Lan parties on and when you really think about it Halo 2 isn't all that different from Halo 3 which will still be kicking it till 2017 when the robot overlords fight the mole people over the matter of who gets to harvest our organs.  
 
It probably has something to do with the fact that Xbox Live and especially Halo 2 ushered in the modern era of gaming. Lets face it, server lists suck, you spend your first 15 minutes trying to jump into servers with a nearly full list of people only to have some jackass on the other side of the internet beat you. Then when you finally get in and become someone else's jackass you probably won't end up on a server you like on the first try. Maybe you'll get kicked out because its people who are waiting for a friend and they don't know how to make a private server or they vote you out. Maybe you'll jump onto a server with custom sound effects, music and maps which has about the same chance as being awesome as it does being terrible, maybe leaning more towards terrible. Or maybe you'll jump into a server with people who have been playing this game for the last 10 years and just end up in a  sequence of 1 second deaths. Yes if you find a good server you can bookmark it and make it your go to server but there is no guarantee it will be as awesome as the first time you found it. 
   
Consistent match making across all games mostly solved these problem, sure if you have a tiny pool of players it didn't work out so well, but if you had a large pool of players like Halo 2 it was amazing. Halo 2 drew a line in the sand and said that we just needed match making, no server lobbies and we would like it damit! Most of us did like it. Sure the match making was molasses fast on day 1 but it was still awesome to be able to join up in a party with friends and just jump from game to game, often being matched with similarly skilled opponents, it was like magic. Being able to jump onto Live with four-player split screen was magic, it was like playing Goldeneye but you didn't have to worry about people seeing your quadrant of the screen because your friends were fighting with you against other groups of players doing the same thing.  
 
We have seen the death of online games before. MMOs tend to be the most interesting to watch as the remaining staff try to put on one last show with no budget for new features. The death of a service, especially something as popular as Xbox Live is new. Anything this popular tends to live on in some form with a small dedicated group of players, but Microsoft holds the keys here. The original Live is stifling the growth of the new Xbox Live and they are pulling the plug. All roads on Xbox lead through Live and if it gets shut off they all die. Games like Mech Assault, Crimson Skies and the Splinter Cell Adversarial mode have no next-gen equivalent, when the switch gets pulled they are gone. Maybe you could tunnel the lan feature to get something up and running, but the community is gone and it wouldn't be the same. 
 
For another blog long in the tooth this is Gametag: Cybexx / Cybexx13 signing out.