Why should it be illegal? You, me, or your neighbor is free to make a football video game any time we want.
If the NFL or NCAA decided to sign an eclusive contract with Nike to be the one and only supplier of shoes to the league/organization, should that too be illegal?
What you're example is talking about is sponsorship...what EA has done is the same as a tire company buying exclusive rights to rubber, therefore making a legal monopoly...sure other tires will be made, but very few will buy them