I went with Royce, Saku, and Nog.
Here's my logic:
For Royce, I absolutely had to include him because he made BJJ known to the world. If we're talking greatness, I think that goes beyond just how good he is and includes his contributions. Of course he would probably lose a grappling match to everyone on that list other than Ronda, but if he doesn't submit all those much bigger, more jacked dudes back in the early tournaments, who knows where MMA would be today. BJJ today is the baseline - it might not be the best base for MMA anymore, but you absolutely have to be proficient in it enough to stop it or avoid it, or you're totally screwed.
For Sakuraba, I had to include him because he took it to the next level by beating the Gracies, and because he used his submission grappling to get wins over much bigger guys like Rampage. You don't get those kinds of size/mass differences nowadays. Rampage was a legitimate top 5 LHW, and Saku would be a modern WW. These days we would never dream of seeing that kind of matchup, yet he pulled it off somehow.
For Nog, same logic as Saku. He fought absolute juiced up monsters like prime Bob Sapp and prime Coleman, weathered the storm and a came up with epic submissions. If you haven't seen the Sapp fight I recommend it strongly. Bob Sapp back then wasn't the guy he is today who takes dives and fucks around to get money. Back then he was pumping every steroid known to man into his body, trained with Josh Barnett, and was the scariest guy in the sport. Everyone back then saw it as a foregone conclusion that he would take over the sport. He also beat Ernesto Hoost in his own sport which is outrageous to think about, given that his technique was just to throw haymakers and be 400 pounds. He powerbombed Nog on his head and beat the snot out of him for what felt like an eternity before Nog armbarred him. Legendary finish.
