I could talk about this for hours. It's a subject that's deep and divisive, and frankly ridiculous. Some will tout the incredible flavors and textures of 'God' shots. It's true that occasionally, an espresso shot will punch me in the mouth, knock me off my seat and leave me on the ground a drooling, shaking mass of awe-struck jelly. But views like these are subjective. The truth is: All coffee is created equal. Any extraction methodology executed well and with amazing materials can deliver a life-changing experience. So why is espresso in such high regard?
Espresso is hard. And expensive.
It takes a lot of practise to pull quality shots, and expensive equipment really will help do it better at a certain point (well beyond where most amateurs are). The pour reacts wildly to small adjustments such as in grind consistency/fineness, coffee quality, temperature profile, dose, tamp, basket dimensions and shape, ambient temperature and humidity, etc. It's very easy to muck up a shot of espresso compared to a pour-over or immersion brew. Consistency is even harder to achieve. For this reason, one measure of a skilled barista is the ability to consistently pull quality shot after shot (rather than the one in three, five or ten that a still-learning barista or amateur might produce).
Espresso is versatile in flavour and uses.
Espresso's potential range in warmth, brightness/acidity, and mouthfeel is useful for a wider variety of beverages (including textured milk combinations). With pour-over and immersion coffee, you can add milk if you like, but the range of varieties of drinks you can make is smaller.
Espresso is the crest of the latest wave.
In the US, fine espresso represents the crest of the third wave of evolution of people's coffee tastes over the last century (the first wave being packed ground coffee and granulated instant coffee, followed by the second wave of Starbucks et al's re-popularisation of espresso-based drinks, followed by the third wave of high quality espresso-based drinks and other fine coffees). This contrasts with other parts of the world (e.g. Europe where espresso co-exists with stovetop coffee, or the Antipodes where espresso gained singular dominance with Italian immigration). As the crest of the latest wave, some might think espresso to be the most up-to-date view of coffee and therefore the 'best'.
None of the above means that espresso is THE best thing. But it's easy to see why people think so.