Brian,
I've been here for 6 years and its has its ups and downs, but overall I enjoy it here. The summers are crazy hot, but the winters are fantastic.
As I mentioned in another post, we've been involved in many of the courses over here so would not want to label any "favorites" over others but I can maybe add a few comments on the one we have not been involved in.
Yas Links usually tops the lists of best courses over here. It's a tough course as the tall grasses are very thick and tough to play out of, but is a very good design, aesthetically and strategically. As a proper links style course, its also completely different then any of the other courses over here (most are desert and/or parkland style) which a lot of golfers here like.
As for the Earth course, a lot of people here prefer the Fire course, and I'd tend to agree, but the Earth has the prestige of hosting the Race to Dubai finale.
I too like the Creek, its a fun course to play and the 17th is a great postcard hole.
I have not yet been to the Royal Golf Club in Bahrain, so can't really comment.