Yes, the slams are the most prestigious of the tournaments, but you shouldn't get a pass from the question at hand simply by winning one or two of them. The question asks who is the worst of the year-end #1 players, not who is the worst of the scrubs. Thus, every player we're talking about is a great player who has accomplished the very difficult and laudable feat of finishing the year ranked #1 in the world. Even the players in this discussion who didn't win any slams, such as Wozniacki and Jankovic, are amazing athletes who did what few others have done - finish a year at #1 in the world. Indeed, it can be argued that it's even more impressive to do that without winning a slam because they didn't get the 2000 ranking points that come with a slam victory (as opposed to, for example, the mere 1000 ranking points that come with winning Indian Wells despite the fact that there is only one less round at Indian Wells compared to the slams and it is a mandatory event so all the top players are there just like the slams). Obviously, the term "worst" is a subjective one, but, again, just winning a slam doesn't give an exemption from that consideration. Valid comparison factors would include overall winning percentage for the year, number of wins and winning percentage against other top 10 players during the year, weeks at #1 during the year, and size of the point gap between #1 and #2 (and maybe the gap between #1 and the other top 5 players as well) which would show the level of dominance for that year. And, sure, some tournament wins are more prestigious than others, so that's a valid factor also, but it's not determinative. (Of course, there's no definitive answer to the question, but it's an interesting one anyway.)