I guess it depends on what's important to you, or how you value greatness. To me, rankings are more important than Slam titles. The tennis season is 11 months out of the year and there is only 4 slams. If a player consistently stays in the Top 10, but doesn't win slams, does that mean he's not a great player? The idea that Slam titles are more important than other titles is funny to me also. It's not like the tennis is harder in Slams. It's the same game no matter what tournament your playing in.
I'd have to disagree, Anny. The slam titles mean everything to the players. They are far and away the four most important events for the year. And yes, the tennis is much harder in the slams. For the men, at least, you are playing best of five throughout, and you also have all of the best players present. Not even mentioning the mental pressure that all the players feel compared to the other events.