CE, by a mile. It was a transformative gaming experience for me. I played a lot of video games from the time I was about 2 years old until my early teens (born in 1980, for reference). From roughly 2013 until the release of Halo in 2001, I wasn't gaming very much. But, my youngest brother and I played a multi-day marathon co-op session over Thanksgiving Day weekend. My girlfriend was out of town, so I had a lot of free time. We started on the Tuesday before, and played all night. My brother skipped school on Wednesday because he hadn't slept, so we played all day that day. This continued most of Thursday and Friday, and to a lesser extent on Saturday and Sunday. This is one of my most dear gaming memories, and an important building block in my relationship with my brother. I'm the oldest of four and he's the youngest, so our age difference in some ways meant we were not as close as either of us was with our other siblings. But, we've shared and bonded over a love of Halo ever since.
Also, it's just a truly great game. I agree that, strictly speaking, it did not establish the genre on console. But, I definitely think it was the most important game in terms of making the FPS genre into the dominant one that it became. Actually, I think it was one of the most important games ever made, in terms of its impact on the hobby.
Bonus: I too hope it is a bit more open. I think the series needs that kind of modernization. But, the most important thing is that it continues to feel like Halo. If the changes take away that Halo feel, then I'd rather it just remain a linear game forever. Even if that means it can no longer be a top-tier franchise. The biggest thing that Halo has going for it at this point is nostalgia. They cannot squander that by changing the feel.








