Halo 1's multiplayer was the best because it didn't have online on the xbox. So every time I played, I played exactly what I wanted. Later, when I played it on PC, it was via a custom games browser, and the results were the same: I played exactly what I wanted.
...just saying. Personally, I'm hoping 343 just ditch playlists altogether going forward. Or redefined them as we know it, anyway (clan or custom playlists via a reddit-like voting system using a "custom playlist" browser with ranks, along with better Forge/Anvil world-shaper tool and deeper access into Megalo for fine tuning sandbox balance).
Edit: Everyone has their own idea of what's the best Halo. It's about enabling players to recreate their ideal experience and then allow them to easily connect with others who share the same tastes. That doesn't mean there couldn't be official ones, too, but the whole custom games thing is a huge fail in that it has hardly changed interface since Halo 2 (aside from Forge, but I consider that a separate feature that plugs into the rest of the game). It's just "too hard" to get them going with even teams, etc, and half the people I play with don't like customs because they don't have ranks/progression.