a few examples of what I find to be off about the new visuals
first of all, some stages either lack real time reflections or the cubemaps of the reflections have been replaced by simply worse looking and inaccurate ones
Notice in the first image, how the reflection correctly corresponds with the hills and mountains in the background, while on PS4 it is a simplified cubemap that does not match the hills in the back. there are just random bumps in the reflection
here a better look on how inaccurate the reflections are in the new version:
and in this stage the reflections are missing almost completely
it was visual flourishes like that that made VF5 and Final Showdown look so "next gen" at the time and which makes everything look so much more cohesive. the game had multiple stages with real time planar reflections, which reflected much of the stage AND the characters in real time. ultimate Showdown has not single stage as far as I've seen with real time reflections
here an example from the OG VF5, notice how much of the background and the 2 characters are reflected in real time using a mix of planar reflections and a cubemap
not every detail is always reflecting, and some stages did not have real time reflections for the characters, but at least they somewhat tried to make them look as accurate as possible given the render budget.
meanwhile in Ultimate Showdown, they either completely removed the reflections and replaced the wet ground with dry ground:
or you have shit like this:
look at this blurry, inaccurate mess!
here the version from Final Showdown with real time character reflections!
and the second part that looks off are some of the characters, here is a side by side of Vanessa:
they completely changed her face for some reason... looks off to me. but not every chatacter looks worse, some look better
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so all in all, the issue I think I have with this version is, it lacks all the ambition the original and Final Showdown had. the meshes might have 10x the polygons, the hair is now not only a texture anymore and the backgrounds have more detail, sure... but if you look not only at the timeframe of release but also the amount of care put into making the game look as cohesive and polished as possible is just not there IMO.
they made extra sure that reflections look as accurate as possible for the hardware in the originals, and the new one just slaps an inaccurate reflection map on water surfaces and replaces all the other reflecting surfaces with matte ones. the original was a truly next gen experience, top of the line... when it released, while Ultimate Showdown looks worse than the average PS4 game