Obsessively social with an adamant penchant for ranked playlists.
Looking for a group to create an XBL TS Reach team. PM me.
That's difficult to gauge as most of play online. The only way to know the quality of one's skill in Halo is to play in a LAN, something that's not within reach for many players.
I would say that a good understand of the engine, and being able to see the flow of the game without needing a visual cue, is a telltale sign that one's become adept at Halo. Also, not everyone is good at all aspects of the game - some people are great at creeping in for a shotgun kill and others are only good at sniping, while a certain group, the majority, is best with a Battle Rifle.
And no, skill levels don't mean anything. I only play Lone Wolves, in which I am a 38, but I take it as "social" and leave my control down, eat while playing, and keep going even if I'm having a bad day and I can't connect a single shot. Others take their ranked games more seriously and only play them when they're focused on winning. That doesn't make them better, but it does translate to a higher skill level.
Personally, I haven't noticed much of a difference between players skill 28 versus skill 42 in Lone Wolves. There's good and bad in both levels. And no, I've never played a 50, but I wouldn't expect much of a difference - unless he's host.