Quicksilver--Leader
Colossus
Storm--Second in command
Psylocke
Polaris
Bishop
Nightcrawler
Beast
I was going to put Phoenix, but I really don't like the acutal idea of Phoenix that much. I really don't like characters that are G0D-LIKE-ALL-POWERFUL. Because, from my understanding of years of following X-men and reading as much about them and owning many comics and such, the Phoenix Force is basically unstoppable, constantly drawing upon the infinite source of energy generated by the universe itself. I dunno why, this just upsets me. There's basically no power greater. I like a powerful character who can indeed still be defeated without having the universe explode or something along those lines.
Same goes for Xavier. And Magneto. Both of them are basically the top leaders of their brand of mutant ability. No one comes close to either of them. And I know this is about making the team as powerful as possible, but that's no fun. It should be somewhat comic-practical, too. I mean, if I just wanted the most powerful team, it would only have to be one person: Franklin Richards. He alters reality. Enough said. Anything he wants, it happens. He's even more powerful than Legion in this since, since Legion is slightly (hah!), well, very psychotic and has multiple personalities, it makes him weak. Franklin on the other hand knows what he has and can think very logically. He would easily be the most powerful. He could just cause an enemy to not exist anymore. Wipe him off the face of the earth. Or he could just have him sent hurtling into the sun. Whatever he wants. It's his call.
Just a good thing he's a good guy, eh?
And I had a hard time deciding between Beast and Wolverine. I know Wolverine may be the better fighter, but I have a team of fighters already. I needed extremely incredible agility, superhuman strength, and of course (probably Beast's most impressive feature), his amazingly vast intelligence and intellect. This team would not be much without a brain on it. And seriously. What team would be complete without a member of it constantly spewing out witty comments/retorts, intellectual comments about classical literature, and incredibly complicated words from his exceedingly immense vocabulary--all during an extremely important, risky, dangerous, and suicidal fight with the enemy? That is definitely a requirement for any superhero team. I dare you to prove me wrong.
And that's my rant for the day. But that's me.