The France international has been the star player for both club and country in 2016. He helped the Spanish capital club reach the final of the Champions League and also France to the euro 2016.
Griezmann's form has seen him attract interest from the Red Devils in recent times. The Sun reports that Mourinho has made signing the La Liga forward as a priority in the summer transfer window.
Arsenal have the services of Alexis Sanchez and Mesut Ozil as the two world class players at the Emirates. Merson believes the Gunners fans deserve much better and advised Wenger to beat United in bringing Griezmann to the north London club.
"They pay top dollar those Arsenal fans. When you're paying that kind of money you have to be watching world class footballers at the club. You can't just have two - you should have five and six in my opinion," Merson told talkSPORT.
"With Griezmann, people go 'they've [Arsenal] got that kind of player'. They haven't. They've got two of them [Sanchez and Ozil], but you could do with another one. For me there isn't a club in the world that wouldn't want Griezmann."
The Independent earlier reported that United remain confident in bringing Griezmann to Old Trafford. However, Atletico president Enrique Cerezo has issued a warning to the potential suitors that the French forward is going nowhere and admitted the star player will at the club for a long time.
"I don't know what the interest of Manchester United is. What I can say though is that Griezmann will be an Atletico player for a long time," Cerezo told Spanish TV show #Minuto0.