LOL, Front242.
This thread has obviously devolved, but one premise from the OP that I disagree with is that the Calendar Slam is the #1 definition of greatness. To me the Calendar Slam is a bit overrated - impressive, certainly, but only a bit more impressive than the Career Slam. They're different in that the Calendar Slam points to a very high level of greatness across all surfaces over a short span of time, but that also provides a limit to it in that it only refers to one year.
It also depends upon the competition. For instance, is Rod Laver's 1962 Calendar Slam more impressive than one of Roger Federer's near misses in 2004-07? (minus 2005). Rod Laver beat Roy Emerson three times and Marty Mulligan once, in the amateur period where the best players like Ken Rosewall and Pancho Gonzales, not to mention Frank Sedgman, Pancho Segura, etc were playing pro. On the other hand, look at Federer's 2006 and 2007 - he didn't win the Calendar Slam in either year because he had to face (and lost to) the greatest clay courter in the history of the game.
We can make the same argument for Novak Djokovic's 2011. In the Slams he defeated Andy Murray once and Rafa Nadal twice, but lost to Roger Federer in the SF of the French Open. Is that less impressive than Laver's 1962?
(Just so you don't think I'm picking on Laver, his 1969 Calendar Slam was in credible; not only did he beat the best in the game to do it--Tony Roche, Andres Gimeno, Ken Rosewall, and John Newcombe--but but he did it at age 31.
As with any statistic or criterion, the Calendar Slam can't be taken in a vacuum (without context) or on its own (without looking at other stats). It certainly should be a factor, but I see it as more of a bonus if you did it rather than a subtraction if you didn't, and thus shouldn't be one of the definitions of greatness.
As for criteria for greatness, I'd look at a few factors, in no particular order:
- Weeks at #1
- Year-end rankings
- Slam wins
- Slam results overall
- Total titles, perhaps weighted towards more significant events
- Career Slam and Calendar Slam
- Peak level (which could include Calendar Slam)
- Plateau level - that is, how good the player was over the length of their career
- Head 2 Head against other top players
Etc
There are more, I'm sure. If I had to tease out what I feel are the most important ones, I'd look at Slam results (both wins and other results), overall titles (weighted), and rankings (#1 weeks and year-end). I think you start with those as the core of a player's greatness then add in the rest as "bonus points."