Like every other game ever made, to me Halo is more fun to play with friends. Even more so when you have friends on your team and on the opposition -- that's why I prefer Custom games in multi-player. I'll still hop on ranked & social plenty of times, but I guess I'm still holding on to the old joys of playing Halo:Combat Evolved on LAN.
With Forge World in Halo: Reach and the customization option set available, there is so much great potential to recapture some of the old feeling from H:CE (and even H2 to an extent.)
Unfortunately, I have a feeling that most of my friend list will gravitate towards matchmaking so they can increase their rank and unlock the armor permutations, custom games falling to the wayside.
Whether there is one already or not, I'd like to start a Giant Bomb Community Group for Reach that wants to play primarily customs. If you are interested, (and plan on playing A LOT) please send an invite to me on XBL. Gamertag: "Jack Colt"
Ideally we can get enough people together who enjoy playing with one another, cross-pollinate each other's friends lists, and almost always have a stable of people available online for some custom shenanigans. Possibly some tom foolery.
And on occasions ballyhoo.
Look forward to seeing you out there!