I don't see how you can say that. Jon, Dany and Tyrion all get as much if not more screentime than Ned.
Firstly, I singled out the pilot episode of each series. Ned is very central to that episode, although it's true that he gets scaled down particularly after he's been captured.
Secondly, This presentation
desginates Ned as our lead. It's quite clear in the pilot and in the episodes that follow that he is the lead of an ensemble - like McNulty on the Wire - and not the central focus of the show the way Tony Soprano of the Sopranos was.
Thirdly, Ned's been present in every episode so far. I can't say the same for Tyrion, Jon or Dany, who have sat episodes out on occasion. The Jon and Dany arcs are also comparatively peripheral to the show's main thrust in King's Landing, which - until episode seven - has Ned acting as the protagonist trying to unravel the mystery of Jon Arryn's death.
If that doesn't make Ned the lead character I don't know what does, and I don't know who
was our lead this past season.