MLS used to be a joke, but in the last 4 years it's gotten much better. I think the big thing is that we are drawing more and more players from Central America, the Caribbean and South American countries. As opposed to some other "lesser" leagues, the teams are well funded, the checks don't bounce and players get paid, the travel is first rate and the salaries are getting better.
The influx of international talent has raised the games of everyone who plays in the league. What I look for is what kind of close control and touch does a player have? You see far fewer passes bouncing 5 yards off the recipient nowadays than you used to.
I would put MLS on par with a league like France or Portugal, or maybe just a bit behind them. We lack the star power at the top that Paris St. Germain has, but the rest of the Ligue Un is full of physical players, good athletes, many who are immigrants from Africa who hope to use the league as a stepping stone to bigger things.
The best leagues are Premier League (depth of talent, good teams halfway down the table), Spain (top 2 or 3 are great, most players are technically proficient), Germany (league is too top heavy, but the talent is there, players defend well and are well organized), Italy (quality of players is down at the top, attendance isn't quite what it should be, club teams underachieve in European competitions and the specter of past match fixing scandals still lingers). That's the top tier, those 4 leagues.
Next tier of leagues, IMO, would be Portugal, France, Netherlands, and maybe MLS? Liga MX would be in here, too. I am not that familiar (at all) with South American leagues, but you would have to imagine that Brazil and Argentina have very good ones that compete at about this level.
Tier after that would be Russia, Ukraine, Greece, Turkey,the next couple South American club leagues, and a couple other Central European countries thrown together in a hat.