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For me it comes down to a three-way fight between Halo 4, Gears 3, and Gears Judgement.
Halo 4's lighting is straight-up orgasmic by 7th gen standards, with gorgeous use of bloom, light shafts, oversaturation, etc to create the sense of a vibrant and striking sci-fi world. Plus I don't recall it's framerate ever noticeably dipping once during my 2 playthroughs of its campaign.
Gears 3 and Judgement just barely edge it out though, as they also have incredible lighting, especially in their excellent simulated global illumination solution, but go one further with more fine texture and geometric detail. Of the two, Judgement ultimately takes the top spot by virtue of slightly better image quality thanks to the addition of AA.
All 3 can hold their own against anything the PS3 ever produced IMO.
I'm with Puggsley in that Horizon 2 and Rise of the Tomb Raider aren't really that pretty due to being squished down from Xbone to 360. They have that "downgraded" look to them.
I do feel an honourable mention is due to Forza Horizon 1 though, now that was a beautiful game.
Rounds out the system's top guns for me along with the three previously mentioned.
