The Xbox was amazing. I still remember playing Crimson Skies on Xbox Live for the first time. It was mindblowing back then that I was playing with people from around the world in real-time. They even displayed the flag of the country that you were from next to your gamertag on the scoreboard, so you could see the country where everyone was from. I couldn't believe that I was playing with people from around the US, the UK and Japan all in a match. And of course, Halo... I can't even tell you how many times I've played system link play with my brothers and my dad. Rockets on Sidewinder was our favorite combo. We ended up getting multiple boxes so everyone didn't screen cheat either. By the end, I think we owned 3 Xbox 1's.
The 360 was easily one of my most favorite consoles, both in terms of hardware (amazing controller) and its games lineup. You also gotta give Microsoft some props on how much they iterate on the OS to make it better. It's been through 3 different major revisions. I don't believe any console OS has ever done this many changes post-release. Plus, with Live on the 360, that's when I really got hooked on Live. Achievements were my crack for a while, and it's now an industry standard with Steam, PS3, Origin, etc all having their own variant of it.
The 360 also has a lot of great apps, and it's now my primary way of watching Netflix and HBO Go. I now use it for general entertainment more than gaming at this point, which is weird in a way. I never would have though it would be that way at the start of the gen.
And love it or hate it but Kinect has been a huge success for them as well, and it really breathed new life into the console mid-generation. For me, the voice controls are the most useful part, since I tend to be watching Netflix or HBO Go more than anything else. There are also some great games for it (Leedmes, Child of Eden, The Gunstringer). A lot of Kinect games are pretty meh, but with next-gen I'm sure a lot of those problems will be fixed (better hardware, software that's being designed for it from the beginning should it should have lower latency, etc).
Can't wait to see what the next-gen will bring.