I think both are composers are good, but the media is vastly different. (I also happen to think both are overrated, but that's something else entirely.) I find Kanno's music to be more accessible, but I think that anime on a whole is more accessible, since a video game requires active participation and not everyone is willing to invest in it.
But all the time spent playing a game makes it very easy for memorable songs to win a special place in a gamer's heart (which is why several leitmotifs appear in every title in either the intro or credits, or as chocobo accompaniment).
Both composers deserve their fans, though not necessarily the sheer amount of people calling them geniuses and such; a genius isn't a word to just throw around casually, especially to composers who are still alive and have many years left in their career. It would be better to compare two game composers or two anime composers; attempting to compare artists who score different media isn't quite fair.