For the record, the MLS is not even close to a top 5 soccer league. It's not the best league in North America and probably doesn't make the cut for top 5 in the Western Hemisphere. As far as Europe goes, the Turkish and Austrian leagues can easily poach players from the MLS, the amount of money being thrown around by the 5 biggest leagues in the world (England, Spain, Germany, France and Italy) is unimaginable for the MLS.
The NBA, the MLB and the NFL are a tier above the NHL in terms of their pull and cultural significance in this country but the gap between hockey and whoever you put at #3 is substantially narrower than that between the NHL and the MLS.
That being said, I do hope the MLS catches up one day but that day is still in the distant future.