You can compare T20, OneDay and Test cricket to Classical, Rapid, Blitz and Bullet chess. At the highest level, players consider them to be completely different games needing different strategies.

It's not just about duration. It's the hardest format in every sense. Test cricket is the format which provides an opportunity for players to reach their full potential. It's what separates great players from the good.

Indian batting great Sachin Tendulkar was going through a bad phase in 2003-04 Test series in Australia. In the first 3 Test matches his scores read 0, 1, 37, 0, 44. He was dismissed consistently playing cover drive outside the off stump. There was a lot of pressure on him going into the final Test match in Sydney. He showed why he is one of the greatest to ever play cricket. He played a genius of an innings for two days where he didn't play a single cover drive shot outside the off stump as planned by him. He scored 241 and remained not out. This is not something you get to witness in an ODI or a T20. Test is indeed the real cricket.

https://www.youtube.com/watch?v=s_P8fpLsi-A

I agree with the fact that there is no "real" cricket but it is not as simple as different rules and duration. T20 relies on momentum, a bit of luck and different set of skills compared to Test matches. That is why you often see teams like West Indies or Afghanistan which can compete with any big teams in a T20 match struggle in Tests.

Test cricket is real in the sense that it is the original game and what we have been calling as cricket until the relatively recent introduction of ODIs and T20s. The shorter formats eliminate the aspects of playing with changing conditions (ball, pitch and weather) which deeply characterized the original game.

Everything but Test cricket just isnt cricket

Analogy: tweets are more palatable than novels.