|Mr Puggsly said:
Everything tends to run better than last gen because is a greater focus on stable performance. Later in the generation we saw greatly improved performance, but you still saw technically impressive stuff like Sleeping Dogs or Far Cry 3 running pretty bad. Meanwhile, GTAV was stunning and maintain fairly stable performance.
You keep saying bringing open world games to last gen was a struggle, but it was done many time over. It also depends on what the game was attempting to do. For example, we've seen Bethesda games struggle when there are too many changes in the world, which is saved in some sort of memory. But the average open world game isn't doing that. Maybe the way Bethesda games did it was also inefficient, their engine(s) aren't exactly praised. The way you speak though games like Assassin's Creed should never have existed on last gen or even improved with each release.
I started playing Gears 3 recently and it especially looks fantastic on the X1X. Halo 4 is the more technically impressive game of the two, because its a larger scale action. The campaign maps are like small open world with lots of enemies, vehicles, etc. It even does that in split screen which is like an anomaly in modern games. Even multiplayer can have up to 16 players on a large map with vehicles, some of the most fun I had last gen. I'm sure it took effort to make all of this work on ~500MB of RAM, but I feel the average game was struggling more with the GPU limitations and were more often pushing the limits of that.
GTA5 didn't run stable on last gen though, it could and often did drop hard when moving through detailed areas as the systems struggled to hustle data in and out of memory. And Assassin's Creed was a series notorious for uneven performance and characters popping in meters ahead of the player. Both were examples of the RAM limitations biting. It's not that last gen systems couldn't do open world, just that it was not their forte since of their three key components (CPU/GPU/RAM) the latter was the biggest bottleneck by far.