I play Big Team Battle almost exclusively, and I'd say the balance for me is running 70/30 with regards to smart players and the short bus.
There's nothing more enjoyable than a back and forth CTF match that ends 1-0 or tied, because both sides have players that are skilled at protecting the flag and reconning various hotspots (the building with the sword in it on headlong, the stony hills in waterworks, etc). It's awesome to work together on offense to gradually get the flag out of a base, into the middle, and then contest it long so that it's close enough to home base that anyone respawning can grab it or protect the carrier.
And then, sometimes, I end up riding along with Louise into a pit, or on a team where all of my teammates leave the base unprotected to go who knows where. What I'd like to know is, what's the gene that makes certain players hop into a banshee and just fly in circles the entire game? Fools. Then again, it's fun to leap off a ledge toward a banshee and take it, and hear some noob say "what the fu**" into the mic. Also have to mention the random lamer who thinks it's funny to kill his own teammates. Yeah, real nice... go play death match, Jr. That's about right too--because most idiot players sound like ten year olds over the mic.
Thankfully, I've played many more good games than bad ones. I'm quite addicted to Halo 2 multi--even if it is basically Unreal Tournament or Battlefield rehashed for Xbox. Fine by me.... there's 60,000 people on at any given moment. Never tough to fill up a 16-player game.