I kinda like the most dangerous game, aside from the obvious cliche of the plot. I think Vaughan is just as good at Millar at characterizing the X-men/other cast, though his plotting isn't nearly as good. That being said, I really didn't love Millar's run, and I'll tell you why:
I
HATE
the dialogue that man writes. I really do. I hate it when girls are called cow. I'm an American teenager, no one calls anyone cow. Ever. I can't speak for Toad, because he's British, or Quicksilver, because he's really high-brow. Ever. And there always seemed to be this formula to the way Millar writes dialogue.
"Oh, character, didn't you know, some random event has been occuring since time period."
That'd probably be followed by the addressed calling someone a stupid cow. I don't know, I shouldn't be ranting, he is a good mastermind, his dialogue just seems so forced.
So, when Bendis signed on, I was uber-psyched. Then it turned out he really isn't that good at writing team books. So, to be honest, I've liked the current runs the best.
Oh, and for some reason, Millar's dialogue in the Ultimates isn't so bad. He still is very formulaic, but less annoying insults.