Going through each slam who would you say is the best to never win it, taking into account ability on the surface as well of course. Some seem fairly easy, while some are tougher. I am going to do my choices for both genders.
Men:
Australian Open- Bjorn Borg, John McEnroe. Not sure if they should even really count though considering the Australian Open was barely considered a slam back then. If not then it is obviously Andy Murray.
French Open- If it was simply best player it would be Pete Sampras, but as I specified your calibre on each given surface should be considered, so that said no way it should be Pete. Even so I am not really sure who the best choice should be here. Most greats who didn't win the French struggled relatively speaking on clay. John McEnroe maybe, only since he was mere points away in 1984. If it is strictly best clay court player to not win the French Open it would be someone like Alex Corretja or Dominik Thiem, but they aren't really good enough players overall to make a good choice. This one is tough to pick someone.
Wimbledon- Ivan Lendl would have to be the choice. He is a major all time great, and was good enough on grass to come close (losing in finals or semis) a whole bunch of times.
US Open- Bjorn Borg obviously is the choice.
Women:
Australian Open- Venus Williams would be the best choice. A major all time great, 7 time slam winner, and a great hard court player.
French Open- Martina Hingis has to be the choice. Venus is not a good enough clay courter to merit being the choice, and while Conchita Martinez and Gabriela Sabatini might be the best clay courters to never win the French, neither is a good enough player to merit being the choice.
Wimbledon- Justine Henin is the easy choice here I think. I am guessing many will say Hana (for being best female grass player who never won Wimbledon), and some will say Seles, but I strongly disagree with both. Monica Seles is not a good enough grass courter to merit being the choice, and Hana Mandlikova is not a good enough player (compared to Justine or Monica) to merit being the choice. Basically best player to not win Wimbledon is probably Seles, with Henin a very close second. Best grass courter to not win Wimbledon is probably Mandlikova, with Henin a very close second. The former (best player) though Hana isn't even top 5 probably, and the latter (best grass courter) Seles is not even top 15 atleast, so Henin is the easy choice as best to not win Wimbledon overall.
US Open- Evonne Goolagong is the easy choice here on all levels. Even moreso considering the tournament was on grass and clay numerous of her years, and she was excellent on both (pretty sure she was excellent on hard courts too).
Someone help me with a best to not win French Open for the men though as I am having a really hard time with that. I firmly believe Sampras is not good enough on clay to be a worthy pick for that, but there also aren't hardly any good options. And people like Corretja, Orantes, Thiem, don't feel like good enough players to merit being the choice. Murray is a better clay courter than Sampras, and a much greater player than those I just named, but he doesn't feel like making sense as a choice either. Becker and Edberg probably are even weaker clay courters than Sampras (along with being less great of players obviously).