contrarian23, with whom I differ only cautiously whenever that happens, makes important points here.
But..I think asking, who was the greater General, Colin Powell or Julius Caesar, Alexander the Great or Napoleon? is a question about how well that general handled what was available at the time and then is about, I think, making an educated guess about how well they would have done under changed circumstances.
To say, Powell calls in an air strike and wipes the floor with the entire armies of the other three, is to assume that Napoleon, Caesar and Alexander would not have been able, given the same time and training, to figure out what to do with air assaults. That is either saying, there are no comparisons possible, which means none of us should be playing on this website, or "there is only progress" - a viewpoint I am skeptical about. Throw some low HR screwball or spitball pitchers from the early years of baseball at today's MLB hitters and a 27-strikeout perfect game is not impossible, and of course we have to ask how well today's HR hitters would have done in some of the 19th century ballparks that had 600 ft. center fields. My guess is they hit .198 with a lot of fly outs.
Shakespeare, were he alive today, would have gone straight to Hollywood and would have dominated there, Aeschylus too. I have little doubt of that.
Beethoven would have composed different music, appropriate to the times, but it would have better than pretty much anyone else's.
The Negro League is issue is more serious: there have been no .400 hitters since 1941 - that is, Williams hit .400, then everybody good, or nearly everybody, went to the army, they came out, baseball was desegregated the next year and there have been no .400 hitters since. Pretty sure the .400 hitter was a phenomenon of segregated baseball, that is of too many second-rate pitchers and fielders, later replaced by the real thing when baseball integrated.
Wagner would have lost some points on his career BA no doubt, all the others too, playing against competition that had been excluded when he played - let's remember that he was an opponent of segregation and a socialist and member of the IWW, so saying that is no slur on his own record. Lou Gehrig and Walter Johnson also both made statements against segregation at times.
But I digress. Wagner with the same training, diet etc. as Derek Jeter, that is what we want to know. Napoleon with an air force. Shakespeare with a $100 million budget and special effects. Beethoven, ah heck Beethoven was so advanced they had to build larger concert halls to fit his music in and the musicians even rebelled, saying they couldn't understand what they had to play. He told them they didn't have to understand. That this music was for the future. He would have had no problem with Duke Ellington composing right alongside him is my bet. He supported the French Revolution after all. Beethoven would have been fine. Here is a piece I had published about him a while back:
https://www.counterpunch.org/2018/04/12/why-we-need-beethoven-in-2018-more-than-ever/