Back to topic then...
It's always hard to compare different composers of different eras and say that one is 'better' than the other. But to me, Beethovens contribution to pianomusic is monumental. His sonates always seems to express some sort of complete idea of life if you know what I mean. I have read quite a bit about him and it struck me Beethoven has had a pretty hard life in many respects. And a strong sense of responsibility and emotion. I feel Beethoven has poured all that experience into his music and composed great works that communicate the reality he lived in. I don't mean to say that he meant to do this, as if that was his goal as such, but I think that is the case with his music. He probably could not do it any other way, being the person he was. I think that is why his music still appeals to a lot of people and remains without getting boring. I think it was Barenboim who said that Beethoven always stays contemporary. I think that is it, his music never strikes me as classical in the sense that it is not modern, or old. To me his music is sort of timeless, hard to describe.
As for the moonlight sonate, it is a great sonate as a whole but overplayed - especially the first part of course - and I think Beethoven is so much more than only this great sonate. The pathetique is another famous one and I think I prefer that one over the moonlight when it comes to his early sonates.