sure, following that argument one could argue ozil plays in a tougher league overall in terms of quality. one could make the typical argument that serie A bar juve and possibly is not up to the level of EPL teams. and ozil has done it before at real. his stats are ridiculous - and always consistent. more assists than messi, david silva, ronaldo, ribery etc
at real madrid he was a beast too. hamsik is a great player, but ozil has done it at the highest level.
ozil assists the likes of giroud btw. no proper striker, give him an out and out striker (like he had when he had ronaldo) or even a decent one - like harry kane or someone and ozil wud be hitting 20+ assists. hamsik has had higuain, who, though not elite, is still an excellent finisher of chances.
also, ozil's ozil's vision one of the best in the world. hamsik is the better goalscorer, but he doesnt have ozil's brain. doubt many do