I always find his vocals incredibly sincere and unique myself, especially in the slower songs like Kings Cross, Love Comes Quickly and I Get Along. I think the fact that he sings everything so clearly instead of doing the whole 'vocal acrobatics' thing makes the songs sound more genuine and real as well.
Anyway, I've never felt 'soul' is very necessary in pop music in the first place. After all Madonna sounds incredibly cold and detached from the music on her most recent album and everyone says it's a fantastic return to form. Kylie certainly has no soul and I'm not convinced she means a thing she sings!
To be honest, I think it's mainly Erasure fans who say this as they seem to think Andy Bell sings a bit like a black soul singer.