Not just the best mutant/x-men on TV, possibly one of the best put together TV shows of the year.
The visuals are amazing, really helping tell the story from David's unique point of view.
The soundtrack is brilliant. In fact the use of sound, or lack thereof, has been incredible through out the show.
If you like Legion I highly recommend Fargo, it's made by the same people. :-)
Not sure about best but it's a pretty good adaptation about David Haller's life. Sans crazy marvel stuff.