The legendary creator of Tetris, Alexey Pajitnov gave an interview for NintendoLife and he (finally) revealed what his favorite block is. Believe it or not, it's J-block.
Here's what he said on that matter: "I have to work hard when I'm on the left corner, so every time, the J-piece is better than L-piece because on the right side I have no problem. I don't know why. Probably because I always rotate clockwise. J-piece is my savior, it's very helpful. T-piece is also very good, but my favorite is J-piece". On the other hand, he doesn't like the O-block that much, it seems - "I don't like the square. It's dumb. You don't rotate it, you don't do anything with it. You don't clear a lot of lines. And you don't get any benefits of placing it". That was harsh, but I do agree with him.
Reading all this made me want to play this iconic game again. Let's break another high score!