Well, I've already got a bloke, but if I was looking for another one, my choice would be based on how easily I could speak to him, how he reacts when I do (is he interested in what I'm saying, or does he just want a good gawp at my t*ts). He'd have to be clean ( ie not spotless, but just not unreasonably smelly or dirty), open-minded and of similar intelligence to me.
For me, it's these things that combine to make a 'nice personality', and things like common ground for conversation, personal views or levels of intelligence will have different meanings for everyone. So the man whom I consider to have a 'nice personality', some women would detest.