Xbox -> Xbox 360 -> Xbox One -> Xbox Series (?). I still don't know whether S or X is the "good one". Compare it to Playstation: PS1 -> PS2 -> PS3 -> PS4 -> PS5. The upgraded line is "PS $number Pro".
Someone can tell me they have a PS5 Pro, and I know what they mean. They could tell me they want a PS6 and I know what they mean, even if the PS6 hasn't even been announced yet.
Someone tells me they have an Xbox One X and my eyes glaze over. Prior to now, that means nothing to me. I don't know when the Xbox One came out, I don't know if it's their newest line, I don't know if X is the Pro or if it's the budget. The S and X may not even indicate pro and budget, but I think they do.
At least Nintendo's names are kind of cute. It's still silly, but at least Wii or Switch is kind of endearing. Xbox Series X sounds like they let an edgy teenager name it; having X on both ends reminds me of the days of xX420ShadowRanger69Xx usernames. Also doesn't make a clean acronym; XSX is both hard to say and makes me think more of SXSW than Xbox.