So far I've refrained from answering because I simply can't, as WinterWind put it, provide a credible opinion. I haven't heard at least half of those listed names play ONE Beethoven piece, much less a significant number of sonatas. However, I have heard both Kuerti and Goode (whose complete set I also have) extensively, and of the two I agree primarily with Kuerti's interpretations; so I'll vote A.K.
Though I'd like to give the honourable mention to John O'Conor...not simply because he's Irish but because he has a perfectly subtle touch for a lot of the sonatas! Of course, I can't say I like some of his sonatas because of this introversion.
One should either be a work of art, or wear a work of art.
You know, some people just have natural talents-like some people play the piano but aren't very tall.