Cannot really say too much about Horizon other than it looks stunning so far. But I do think FFXV looks way better than Watch Dogs2. AC Unity looks great for sure, but only as long as we're talking still images. As for whether the engine's gonna be lucrative or not: who's to say there won't be a XV-II and XV-III this time. There's certainly a ton of dlc planned already. As for Unreal Engine 4: The very few games which were developed using it at this point don't exactly paint a very rosy picture. Most of them are tiny-ass indie games which looks like crap for the most part. The few bigger ones like Street Fighter 5 and Tekken 7 look no more than decent either (technically speaking that is. I think SFV looks great, but that's really due to its art style.) Compared to what Rocksteady and NetherRealm studios accomplished with UE3, those results are kinda pathetic really. Gears 4 is the big exception here, but it's also a straight forward corridor shooter.
As far as open-world games go, FF XV looks pretty damn impressive to me. Seriously, how many open-world games manage a seamless transition from exploration to God of War 3 style boss encounter. Then there's all the little details, like the way the magic grenades affect the environment (one particular summon really takes this to a whole new level). In terms of animation the game's in a league of its own as well.
