You guys are missing the point here. Compare Hellblade and Devil May Cry 5 on PS4 for instance. Devil May Cry 5 has better materials and volumetric effects, lots more enemies on screen and they look comparable in other areas, but Hellblade is running at 30 fps and DMC at 60 fps. Same for Xbox One X, they might run at the same framerate but to achieve that Hellblade is running at much lower resolution than DMC. DMC looks amazing while NOT sacrificing either resolution else framerate, which is why the engine is impressive and nothing on Unreal Engine has achieved the same.
In what we currently have had hands on with, the base Xbox One struggles to get to 60 fps and isn't there consistently enough for the 60 fps cap to be meaningful. Granted, this is pre-release code that's definitely months old but it's all we have to go by.
In addition, as others have stated, the teams using UE4 generally have lower budgets and development windows (which might be why they're using an off the shelf engine instead of developing a proprietary one in the first place) so the output of UE4 is skewed to look worse than the engine is actually capable of. Yeah, it won't get to the point of something that's purpose built for the features it's going to use but it will get fairly close when used well (80-95%).
But it's also disingenuous to say something that's 1080p60 is automatically technically superior to something that's 900p60 with 1) little description of the actual effects or quality (i.e. sampling) of effects enabled as well as speaking to how well that 60 fps target is consistently hit. Something can use a lower number of samples but be tailor made to produce a certain look that ends up looking better than something that's more technically demanding. This is where the purpose built nature of proprietary engines makes the difference. Even so though, UE4 has found fairly good uses to fit your goal posts set in this thread. SF5 and DBFighterZ both hit 1080p60 with next to no issues on base PS4 and show the engine's flexibility to artistic expression and effects. Deracine also hit lofty goals using UE4 on base PS4 hardware used for VR. Ace Combat should be 60fps as well (not sure about resolution). And of course there's Fortnite, GRID, Injustice 2, and Lawbreakers that all manage that target, and the upcoming Mortal Kombat 6 and Jump Force that are aiming to hit 1080p60 with some pretty incredible use of details and effects.
Finally, when it comes to GPU tech I've personally experienced better performance in UE3/4 when using nVidia hardware vs AMD hardware and I'm not alone. This adds an additional skew when it comes to UE4 on consoles, meanwhile the Switch is doing quite well with it (see the new Yoshi game and Snake Pass on Switch vs PS4 scaling better than most other titles).
These are just all things to take into consideration before making a generalization that UE4 is "a failure".