For those saying free cloud saves. How? I don't pay for Xbox online and it never saves my games in the cloud.

100% agree with you. It was an influential move for sure, but it makes me unhappy about online play on all consoles, and I remember very well who is to blame for that (doesn't mean the others are without blame either, of course). From a gamer perspective, that's one of the worst things Xbox has done in its existence due to its influence.

It played a huge role in moving me to PC.  $500 console, plus another $500+ to play online...  at some point the cost of online buys a GPU.  Then classic games being behind a subscription, that broke the camels back.  Consoles arent cheap anymore.  

Yeah the controller is one of my picks as well, the 360 and XBO pads are for my money two of the best controllers ever made, so comfortable.

I think PC became my main platform regardless of the cost of online gaming on consoles, but if I hadn't made that decision yet, the cost of online gaming would definitely affect my choice of main platform now.

Free cloud saves is a huge one, and it being seamless through their ecosystem was amazing. Playing a game on console in the living room, and then going into my room, booting up the game through cloud gaming on my laptop and continuing where I left off, is fantastic.

The design of (most) of their consoles. They really have good-looking consoles: the Xbox 360, Xbox 360 S, Xbox One S and X, the Xbox Series X... all look very appealing to me.

The controller layout with the joysticks is the best.

I liked the green cases

Yeah I quite like their console designs too, the Xbox One S/X and Series X especially look so sleek and cool.

Since it seems a lot of the stuff I was gonna go with has already been taken I'll go with something a lot of people don't think about.
Microsoft with the Xbox and Xbox 360 bridged the gap between porting games from PC to console and vise-versa. They got primary PC developers to make games for consoles because they made their consoles more like PC's just a closed PC. Development between the two was no longer apples and oranges.
So I think what they got right was bringing a lot of PC only games/series to consoles and made their consoles developer friendly. If you think about it the Xbox and Xbox 360 were the easiest consoles for developers to make games for during their time.

Well DC was doing that with the support of Win CE. It got a lot of western ports from PC because of that.