Ok, I've played all three systems, and seen others play them. I still personally like the GameCube best out of all of them (Rogue Leader is awesome), but they're pretty much equals when you balance everything out.
For the graphics, I can honestly say I noticed no difference between GameCube and XBox. They are both a step above PS2 in graphics, but that is to be expected, as PS2 is using chips that are a year older.
The controllers... GameCube and XBox controllers are an improvement over the PS2 controllers, but they do have their faults. GameCube has a trigger on the right side just above the analog control on the top; I didn't even notice it was there until the end of the night. The 'B' button is also a little awkward, being a lot smaller than the 'A'. Overall, it is a very good design, and a good size. XBox is also very good overall, but it is HUGE, just like everything else with the XBox. The black and white buttons would be better suited as a second set of triggers, as you can't really use them without taking a hand away from something else. The PS2 controller, I didn't really use... from previous uses, it is good, but I find the GameCube and XBox controls more comfortable (and all are an improvement over Atari or NES controllers
).
As for the games, I have to say that I am very impressed with Halo. I still don't agree with certain friend's claims that it will utterly replace HalfLife, as they occupy different niches in the FPS genre. The graphics are awesome, the AI is nearly as good as a human (they hide in corners, cover each other, team up on you, etc.), and it is just as fun to watch as it is to play (especially the Last level). Rogue Leader lived up to expectations, and I had a bLast doing the Death Star trench run, after I figured out that up=down, and down=up, but right=right, and left=left
And those two games took up most of the evening for me, I saw NHL 2k2 for about 30 minutes, Obi-Wan for about 30 minutes, and I was helping bLast the Covenant while others played SSX Tricky, WaveRace, and Madden.
One minor note to add: The XBox froze five times throughout the evening, so there may be some issues to work out there...