Ryze is not a counter to Ahri people. A counter actually has the ability to gimp the champion they counter. Ryze doesn't gimp Ahri, he just doesn't get run over like it's nothing. Ahri can still farm in complete safety and there is nothing Ryze can do about because 675 range is not enough to deal with her. If she stays safe you cannot get close enough to harass her without telegraphing it and eating a Q to the face.
The only champ I know of that can deal with Ahri effectively excluding Kassadin who is a counter to AP mids in general(though he still loses until level 6) is Swain.
Suffer_Not posted... Kat is a hard counter because you just shunpo to minions and avoid every skill shot.
Morgana is a hard counter because spell shield to avoid charm and Ahri doesn't do any damage.
Same with Sivir.
Basically anyone who can avoid the combo somehow cannot lose to Ahri without jungler intervention.
Morg is not a hard counter to Ahri. Why do people think a shield that only absorbs 95-150 magic damage for the first 15 minutes of the game makes her invincible? Ahri can farm just as easy as Morg can with her Q.