Absolutely horrible comparison.
Juan Gonzalez was one of the best outfielders of his era. He had a long 16 year career. Not only hit for power, but had a career batting average of .295.
He won two American League MVP awards.
Nothing about Joey Gallo's resume stacks up or resembles anything close to a player like Juan Gonzalez at this point in their careers.
After a quick look at his stats, one thing looks weird.
In his final 2005 season, at age 35, he played one game, had one at bat. What's the reasoning there, some kind of farewell tribute or something ?