Why not both?

I was a Sega kid growing up. I owned every readily available piece of Sega hardware, except the Nomad. I loved Master System and Genesis (bought it several days before it was supposed to be release). Loved Game Gear. Didn't care much for Saturn, but had a lot of fun with Dreamcast. These systems, along with Atari 2600, are what made me a gamer. I really loved Sega as a kid.

As an adult, though I have owned every major system except for Vita, probably 80% of my gaming has been done on Xbox. Mostly that's because of Halo.

Over the days leading up to Thanksgiving 2001, My youngest brother and I did a multiple day marathon Halo session. That Marathon session is, by far, my fondest gaming memory. Because we were pretty far apart in age, I wasn't as close with this brother as I was with my other siblings. But, at that time, and in the decades since, gaming has helped us bond with each other. So, I wouldn't trade that for anything.

Luckily, we don't have to choose between Sega and Xbox. Their history, at least in the hardware space, doesn't overlap very much. There never really was a time where we had to choose between them. And, we certainly don't have to do it now.

If I were you, I'd just pick up a Series S. A whole lot of the Xbox back catalogue is playable there.  If you think you'll use it a lot and don't care about the extra money, spring for an X. But, if we're talking about playing a few highlights from the last 20 plus years of Xbox output, your experience will be 99% as good with an S.  

And when you get one, I think the first thing you should do is play Halo CE, whether you like shooters or not. That's such an important game in the history of the hobby. Everybody that loves gaming should play it.  

I’ve got the Series X (snagged it at a 50% discount back in June), though I have yet to even unbox it. Halo CE sounds like a good option, I’ll look into it.

(im realizing my og comment may not fit here too well lol. Might just open a new thread here asking for recommendations or smth.)

My favourites are everything (NS, XBSeX, PS5) expect PC and Mobile!

Sega any day of the week.

To me, Sega is alt-Nintendo. It feels like the cooler, hipper version of the same thing. Xbox is owned by Microsoft, and it's always felt like it. Sure, the first two Xboxes were great, and the libraries were as well, imo. But it always just felt like a PC under the TV; an agnostic box; a means to an end etc.

I choose Sega.

I never had a Sega console, and have owned one Xbox console in the Xbox One S. I would still go with Sega as the Genesis to me is an iconic console. The 360 certainly had it moments coming out early and cheaper than the PS3 with solid exclusives and timed exclusives. None of the legacy Xbox games are up my alley Halo, Gears Forza games. I do like a lot of the rpg's that Sega made back in the day, although I hadn't played them until years later.

Never owned a Sega console and grew up playing Xbox so an obvious choice to go with Xbox.

What the hell are you waiting for? Open it and play some games. You're missing out. 

Yeah Sega do fall closer to Nintendo stylistically, which goes a long way with me as a lifelong Nintendo fan. On the flipside, I do feel like Xbox, at least in the OG/360 days, better suit my tastes at the time software wise with stuff like Halo and Gears, which provided a nice contrast to Nintendo's stuff.

I miss the days of Sega hardware to be honest, their consoles had style where, as JackHandy says, Xbox (and PS) feel more utilitarian.