Well, my first experience with it was watching the multiplayer way back in High School, but it wasn't until college when I got my hands on the Single-Player itself. It had very smart AI, and an absolutely massive setting that honored the sense of scale. Just look up, and you see the enormous space ring in all its glory. They also found clever ways of making console FPSes work with minimal-auto aim tricks. I typically avoid auto-aim at all costs, but they made it work. The storyline never impressed me(It's like Starcraft, but as a First-Person Super Soldier or something cause reasons), but it's not what made the game great for me. A bit like with Mass Effect, the combination of exploration, the fresh take on combat, and the atmosphere itself sold me.
...and like Mass Effect, my interest kinda petered out around Number 3. From what I saw from playthroughs, they did a strong job on 4, and I'll keep my eyes on 5. Like Chewin, I'm avoiding X1 and sticking with PS4. They might get other ports, but I wouldn't hold my breath.