Heard Gibbons play a lot of Alkan so he's no. 1 in my books.
Only heard Maltempo & Hamelin play the Le Festin d'Escope, but Hamelin easily bested Maltempo in that piece. Maltempo struggled to maintain the tempo in the piece with the squigly demisemiquavers and the semiquavers in the LH; HOWEVER I did watch a video of him playing all 12 Etudes in concert, so I have to admit - that's one HELL of an endurance challenge.
Hamelin however played the piece without breaking a sweat.
I've heard John Ogdon play piano, but not Alkan.