Ok so I'm glad we can agree that to be a truly great player you need the complete package. But I still think you are underplaying the importance of having a great serve. Let's talk for a second about players just below the level of the greats who are trying to win a grand slam. I'm going to go back to my other post about how a grand slam winner will usually win 60% of their games (there are almost no outliers to this figure) and let's think about how they can reach that number.

We have a great example of two players with contrasting styles who are right next to each other in the rankings: Nishikori and Raonic. I won't use Wimbledon as the example as the grass obviously favours Raonic a lot, so let's look ahead to the US Open an asses how each of them will have to win the title.

Raonic wins 92% (holy moly) of his service games on hard courts. Nishikori wins 79%.

If we assume at the next US Open they both serve at exactly the same level as their career so far then this means, to reach our magic number of 60% games won, Raonic will have to break serve in 28% of his opponent's games. Nishikori on the other hand will have to break in a ridiculous 41% of opponent's games. And when he reaches the latter stage of the tournament he's going to have to do that against great servers like Federer/Djokovic or even Raonic himself.

So how can Nishikori even hope to win the US Open? Well ironically the only answer I can see is to serve lights out and win 90% of his own service games. He just has no hope of breaking that much against top quality players across multiple rounds. (in 2014 he broke Djokovic 5 times but then lost to, you guessed it, a big server in the final)

And that is why I would always put the serve as the biggest asset a player can have. It just means you have to do so much less work when the ball is at the other end.