Yes, the sale of games with mature ESRB ratings should be legally restricted to adults, because we limit sales of things that might be inappropriate for children. We do not sell children alcohol. We do not let them buy R rated movies. Parents need to be able to exercise oversight over dangerous things that children might get their hands on.
The sale of games with "mature" ESRB should ratings be legally restricted to adults because their content can be quite dangerous to growing and under-aged minds. Sales should be prohibited to those under 18 or even those under 21. The human mind simply does not have a fully formed brain for proper decision-making under these ages.
Legally, ESRB games with a "mature" rating should only be sold to adults ages 17 or older. That's because imagery in those games can be too intense for younger children. Splurting blood, nudity and gore aren't appropriate things for younger minds to see quite yet. Ratings are there for a reason.
No, the sale of games that are labeled mature should not be restricted to only adults. These games labeled mature include things like Call of Duty, which are extremely popular among the teenage population, so the game companies would lose to much profit by only allowing adults to buy them.
Adults are old enough to decide what kinds of content they want to be exposed to so they should be able to buy mature rated items whenever they want. We don't need to ban and restrict things from adults. They are old enough to make those decisions for themselves already.