Everyone keeps talking about how powerful Storm is. And that's great and all. But look at it this way:
You and I are standing in a field of combat, you are armed with a thermonuclear device and timer, and I have a twenty-two.
Who has more power? Clearly, you do.
However, your thermonuclear device has a ten second timer before it goes off.
If we were to fight, who would win? Certainly, I would be able to shoot you in the head long before your nuke detonates.
Alternatively;
Say there is a superhero who's power is the ability to create cosmos. Infinite amount of stars, planets, galaxies, etc.
However, that's his only power. He'd still lose against say...classic quicksilver, just because Quicksilver can function at speeds greatly surpassing our cosmologist. Even though the cosmologist is OBVIOUSLY the more powerful - able to create entire galaxies.
One MORE way we can look at it: Two boxers each have a knock-out punch. One of them practices it on the speed bag, one on the heavy bag. Who is gonna win in a fight? Clearly, the one that can deliver it much faster will.
For Jean Grey, Telepathy OR Telekinesis (either would be effective on Storm) happen INSTANTANEOUSLY.
Not in half a second.
Not in a heart beat.
Not in the blink of an eye. But INSTANTANEOUSLY. Grasp the difference.
Jean Grey wins. I don't care if Storm generates enough power to send the Delorean back in time or not, 😉.