Sabbathia is allowed to be wrong.
Ohtani is unique. Doesn't make him the best player in history. He's not the best player on his own team...though to be fair, he's had a pretty good start offensively this season.
Ohtani might make the Hall of Fame. He's got a LONG way to go though, especially considering he's about to turn 29. He currently has 145 career home runs and a .269 batting average. Pitching? He has a career record of 33-16. A guy his size would likely start to fall off a cliff at age 35, so he's got 6 more good seasons in him. He might not get to 400 career HRs. Not a great stat in today's world, ESPECIALLY if he doesn't improve upon that dismal career batting average of his. Pitching it's even tougher for him. He's only had ONE good pitching season so far, though he has had a good start pitching this year.
He definitely gets some bonus points for being a starting pitcher and a starting offensive player, so if he can approach even very good stats in either of those things, he MIGHT get into the Hall of Fame. Personally, I'm not sure VERY GOOD stats in both should be enough. He's not as good a hitter as Carlos Delgado, and he won't have the career stats there that Delgado has, and Delgado isn't in the Hall of Fame. He couldn't make it stand alone as a pitcher either. He has 33 wins!
A lot of hyperbole surrounding Ohtani.