Selene is much older then Apocalypse right? And I'm sure she's much older then Namor too.(Who claims he's the oldest mutant)
IMO Selene takes this, she has too many powers, plus she's an above average telepath.
"Able to manipulate inanimate objects; telekinesis; hypnosis; able to psionically drain life force to retard aging process; can assume shadow form. She can also wield magic to a devastating affect and can use it for various uses. Telepathy, pyrokinesis, enhanced strength, superhuman speed, near indestructability"
Agreed, Emma is a better telepath, however Selene has a type of superspeed, it seems more like teleporting IMO. With that and her superior strength, not to mention her disturbing TK abilities, hypnosis, life draining ability, magical abilities and near indestructibility it's hard to see Emma taking it.
Unless Emma is able to defeat Selene telepathically before she's able to pull out her little arsenal of powers.
(Must not forget Sage)