I don't understand the point of the tattoo insult...
It was posted in "AwfulTasteButGreatExecution", a subreddit for art that's done well, but is kinda weird. So, he's saying the tattoo is good-looking. Maybe just isn't the best taste, I guess? Lots of people have tattoos of their wife...but not Ian.
But, that aside, compare the two:
Ethan has a tattoo of his wife, and maybe more?
Ian has... Random tattoos?
When Ethan roasted Ian's tattoos, he said they held no meaning, and they were just cool pictures he saw. He didn't directly say they looked bad. So Ian implying that Ethan's is bad, because it's of his wife just makes me think Ian thinks it's stupid to love your wife. It's dumb to comemorate the love of your life on your body, with a permanent marking, sacrificing that slab of skin directly with her image. That's why he won't get Anisa tattooed on him.