Cant compare..... Lou played when there was about 12 teams,only white players were allowed to play most of them with jobs outside baseball,and nobody threw over 80 mph,and just curves and fast ball (piece of cake by today's AAA standars).......dont get me wrong i have the greatest admiration for the legend.
There were 16 teams, almost 50% less than now, so the fact that only white players is balanced out. Today there are a lot of Hispanic and some Black and Asian players, but twice as many teams, so the overall quality is the same.
Today, there are not enough good pitchers for all the jobs in the majors. Back when Lou Gerhig played, only 4 man rotations, sometimes 3, and most pitchers completed games. So you faced the cream of the crop all the time. There were no speciality closers, but hitters didn't get the advantage of facing middle relief pitchers that shouldn't be in the majors like today.
And Bob Feller was proven on film to throw 100mph. Plenty of hitters faced Walter Johnson and Feller in their career. And said that Walter threw just as hard as Feller. So there were pitchers who threw 80mph, 90mph and 100mph during Ruth and gerhig's days. Plus you had to face these good pitchers for all 4 or 5 at bats in a game. There are probably more hard throwes in todays game, but they are all babied and put on pitch counts by their agents, and only pitch once a week. Hitters back then also didn't have the benefit of video training, let alone ped's.
Plus, skuffing the ball and puting foreign substances on it were common, and not enforced back then. Balls were used until they were lost and not as lively to begin with. And ball parks were much bigger back then too. Everything is relative. If you dominated an era, with everything being equal for the rest of the players, then you were great. Gehrig was not the all around athlete that Canseco was. But if Lou would have been born in the mid 60's like Jose, and used everything he did, Canseco couldn't hold his Gerhig's jock as a Major Leaguer !