How can you choose Gambit or Beast over Storm? If we're counting out Wolverine (since he wins by default in any "best" list), then Storm is the clear winner.
She controls lightning with her mind... think about that.
So in "Best Marvel Character" you choose Wolverine?! Pffft! My 5 favourite characters are all better than Wolverine... Doctor Strange, Captain Britain, Cable, Pete Wisdom, Iron Fist. BOOM! All better than Wolverine, though Iron Fist and Wisdom probably couldnt beat him in a fight nine times out of ten but as characters they are more interesting. Dont get me wrong, I dont hate Wolverine... just dont think he is the best.
I do hate The Sentry though, UGH! Glad he got killed off, stupid Diet Superman.
Best X-Men member? Of all members??? Well...
In all seriousness, however, I would have to say either Cyclops or Magneto...
That would be a great answer, except he was never a member of X-Men. He was a member of X-Force, but never a member of X-Men.
I'm actually a pretty big fan of some of the more odd choices for X-Men, like Dazzler, Pixie, and the most powerful X-Man of all time, Iceman. He hasn't actually learned the full extent of his powers, and most people probably won't figure it out, but if they decide to run him at his actual full power, nothing could stop him. Negative Entropy is the ultimate extent of his powers. Once he gets there, it's just over.
Cable could, Doctor Strange could... just saying.