Where velocity is recorded on the journey from the mound to home plate makes all the difference. Take Aroldis Chapman, for example.
www.baseballamerica.com
Just a tidbit from that link:
The moment a baseball leaves a pitcher’s hand, it starts to slow down because of drag. According to University of Illinois physicist Dr. Alan Nathan, a pitch that leaves a pitcher’s hand at 100 mph will (at sea level) slow down by 9 to 10% by the time it crosses the plate some 55-58 feet later.
So that 100 mph pitch could be measured at 100 mph (at the pitcher’s hand), 99 mph (at 50 feet from home plate), 94 mph (midway on its journey) or 91 mph (as it crosses home plate)—the rate of decrease varies based on atmospheric pressure, so a pitch at the altitude of Denver’s Coors Field slows less than a pitch at Tropicana Field in St. Petersburg, Fla.
For decades, comparing pitch velocities has often been an apples-and-oranges
The current MLB Statcast system measures velocity as the pitch leaves the pitcher’s hand.discussion. The first radar guns that began appearing at ballparks in the late 1970s and early 1980s measured pitches much closer to the plate.
My two cents: Nolan Ryan was recorded throwing 100 mph in 1974 with the old radar guns. That could be approaching 110 mph which is way faster than anything ever recorded in modern day history. The fastest on record is 105.8 but that is still way slower than Nolan Ryan and Bob Gibson never was measured. Both would dominate today's game just like they did back then in my opinion.