I've seen a lot of things change over the past 10 years. I watched the community in it's infancy, and seen the culmination of what it is now. As stated previously, a lot of the community was made up of 20-something guys and some in between 13-17. Taking a look at the community now, a lot of us have grown up and moved on, or have had our play time sevearly deduced.
There are a couple things in my opinion that have lead to the slight decline in the community.
#1. Lack of PC support. As the community gains newer younger members, most parents are not in a rush to spend money on a console simply because their kid wants to only play a Halo game. I have seen this before when playing Halo PC. Most people on there have not played Reach or halo 3 yet becuase their parents wont let them or spend the money. Brining Halo titles to PC would open up the market a bit and give COD, Gears, BF a run for their money and allow younger community members to play newer titles.
#2. As previously stated again, the game market has caught up. It took a while but it happened. Halo no longer holds it's own in the FPS market compared to the newer and better formatted games around. Games like Crysis have outdone Halo in terms of LOD and poly count for models. This allows a better visual experience.
#3 World economics have played a huge part in the declining video game sales this year and prior. People have limited amount of money now, and when deciding to make a purchase, want to ensure their purchase has significant replay value as well as a long time coming support and expansion system. In terms of support, the entire CoD and MW series has Halo beat in terms of new added content. When faced with a choice.....loads of content plus new content vs silly new achievments......the bonus content and future content coming, will always win out when a purchase decision is made.
#4 An overlooked and understood portion of the video game world is the dreaded 7 year gap. That is the time in which it takes software to fully complete it's uphill to run to match and properly support the hardware market. When the 360 first came out, the software the game companies had to work with as well as Microsoft, was bleak. The hardware the 360 ran on was not fully supported and lacked full features and abilities that we see in games like Reach and the upcoming BF and CoD titles. Unfortunately for everyone, game companies don't make money just sitting around waiting for proper or better software so they can make a game. Sometimes we just get stuck with a sub-par title or things we don't like. Beleive me, I am sure Bungie would have loved to have made a great ending Halo title that brought the 360 to the very brink of exploding, but the support is just not there yet. it's almost there...almost. This is another reason why the Halo ciommunity has seen a decline. When newer games come out, they have benefitted from ahving a better development resource base. Reach was mostly finished up in early 2010. Development for it basically ran from early 2009 to 2010. Games like BF and MW3 have had production times ranging from 2009 to 2011. So obviously they have had a better support base for the consoles in terms of development tools.
I do believe however, that Halo 4 will be the title that re-ignites the Halo community to it's former glory. When H4 makes its appearance, it will be utilizing DX11 or possibly DX13 shader and xenonlib support, which is just about bursting the seams on the 360 hardware. We should be provided a game that has the best resource pool to choose from and it should be able to deliver a visual expereince like we have never seen before. Also keep in mind, that since this is 343i's first standalone linear Halo title...we are still unsure of how well they will keep the map files encrypted. I hate to say it, but modding and hacking can really breed a huge community. If not for the myriad of Halo 2 apps that we had to mod, change and rebuild map files, it would not have been as popular...that is a cold hard truth.
Is it just me, or do all my posts seem to turn into a novel of sorts?!?