It adds more romance to the game, more potential for the giants to fall and adds to the drama and excitement that has made this sport the world's game.
However, besides a more enticing plot and the possibility of new, untold chapters being written into the annals of football, the presence of United and City, two European superpowers (albeit in terms of money as regards Man City), in Europe's second tier brings huge benefits to football in general.
Here's how their participation in the Europa League will improve football.
The presence of Manchester United and Manchester City will no doubt give the Europa League added prestige.
Great sides with star players in the modern game have graced the tournament in the past, most recently Bayern Munich and Liverpool.
However, this time around, the competition becomes more star-studded than ever, with the champions of the world's most popular league and the world's richest club involved.
Star names like Sergio Aguero, David Silva, Wayne Rooney, Javier Hernandez, Yaya Toure, Nemanja Vidic, Nani, etc are all in the tournament and have expressed their desire to win it.
That adds a new-found prestige to the Europa League, which in turn creates a better product for both the players and the fans, which of course is nothing but good for the game.
The absence of Manchester United and Manchester City from the Champions League will help other less-advantaged teams progress.
And that's another good thing for the game, with more league champions (and that's what the tournament is about: creating a league of European champions) given the chance to progress further.
The likes of APOEL Nicosia (Cyprus), FC Basel (Switzerland) and Zenit St Petersburg (Russia), all champions in their respective countries, will have a better shot at reaching the quarterfinals and perhaps further.
This in turn will improve their finances, brand equity and help them become stronger clubs in general, helping the Champions League achieve its aim (i.e. creating an exclusive club of the best teams across Europe) and boost its integrity with more actual champions and worthy teams in the competition.
FC Barcelona's stranglehold on the Champions League could end within the next season or two following United and City's exit.
Why? Because the Champions League now looks set to become a more competitive tournament with teams across Europe no doubt given hope by the achievements of Napoli, Basel, APOEL, Zenit, etc.
The falling of such giants as the Manchester clubs will most likely instill a greater belief in the "smaller" teams. If United and City can be beaten, what's stopping the likes of Barca and Real Madrid from also getting toppled?
After all, football is a game of 11 men against 11 men, all human beings with no magical abilities that can't be achieved.
That sort of optimistic mindset, which was evident in the likes of Basel, looks set to become more prevalent in the Champions League, which in turn will make for a more competitive, exciting competition.
The presence of two of the biggest and most prestigious teams in the world, and the superstar players they have, will undoubtedly boost TV ratings for the Europa League.
That in turn will get bigger and better sponsors involved, offering more money and boosting the UEFA coffers massively.
This will ultimately mean a greater prize money available for Europa League teams, greater TV money for all involved and will give teams from smaller countries more money than ever to financially compete with the big boys in Europe.
And that, like all the other benefits that will come from Manchester United and Manchester City playing in the Europa League, will be nothing but good for football.