When the Xbox One was announced, people complained that it was confusing, but really it had been long enough since the original Xbox that the name was just silly, not confusing.

The One/Series S/X crap is genuinely baffling, totally incomprehensible unless you've really been keeping up with every Xbox release. You can go on Wikipedia and figure it out in a few minutes, but...you should not have to do that.

Don’t forget the OG offender in this category, the PSOne / PSX

In Sony's defense, everything else with the PlayStation was actually pretty straightforward. PS1, PS2, PS3, PS4, and PS5.

"PSOne" was a weird way to brand a slim console, but it's still obvious that it's a PS1. And while Sony did originally use PSX to refer to the PS1, that was an internal codename, i.e. "different from the Nintendo PlayStation[0]". The gaming press ran with it because people in that era insisted on awkward three-letter acronyms for all games consoles. Reusing it for a weird PS2 DVR combo unit is still way better than Microsoft launching two different consoles with the same name.

[0] The cancelled SNES variant with the also-cancelled Super CD add-on built-in, both built by Sony.

The order is 360, One, Series.

The letter is just tier.

It's remarkable how thoroughly they managed to outdo the confusing nature of "One". Who would look at "Xbox Series" and think that's the name of a specific generation? It's an artistic masterpiece.