There's never been anything quite like the Marvel Cinematic Universe in the history of cinema. It's not just an ongoing series of movies, nor is it as many state a series of interconnected movies; it's an interconnected fabric of several smaller franchises that all thread together to form a bigger whole.
That it's been pulled off, with few-if-any major slip-ups, is nothing short of a miracle, showing the extent of understanding of source, audience and basic blockbuster filmmaking at Marvel Studios. At their best, the movies function on three distinct levels - as standalones, as part of the subject character's arc and as a small puzzle piece in the wider universe - representing a shift in how rollover franchise films traditionally operate (on a side note, it's this factor that has made it so hard for rivals to replicate the success).
So while much of the focus on this mega-franchise tends to lock on the big picture, it's important to remember that the MCU is made up of several, smaller (read: regular size) franchises, each one both a spectacle by itself and a cog in the bigger machine. It's the focus on these multiple purposes that has led the series to become the highest grossing franchise of all time in less than a decade, and ensure new adventures feel fresh even after thirteen new movies.
With that in mind, let's take a look through these various strands and see how they hold up on their own, ranked from worst to best.