The reason is simple: Smash Bros. IV lacks lighting, it's like it has very minimal light sources, almost like they're using an updated version of GC / Wii lighting. It's colorful sure, but the lack of precise lighting like MK8 is what makes it look factually less impressive technically.

First you say:

So, if those series have always been extremely successful both commercially and critically and they were never really known for impresive graphics, then impresive graphics are not really expected for them and that's fine. They more than make up for it in gameplay excellence.

So then, why are you complaining about SSB's graphics calling them "dissapointing"?

Mario Kart and Smash Bros have very different goals with their graphic presentation. Mario Kart involves you being in a close third person, where small details have the chance to pop and matter quite a bit. Smash Bros. by comparison, involves being able to visually digest an entire arena and represent unique attacks from a variety of distances.

While looking at screenshots of Smash may not be as impressive, almost all of them are zoomed in closer than regular gameplay will be. Zoomed in footage makes sense for focusing on what trailers and screenshots are trying to highlight, even if they don't represent the ordinary gameplay angle.

You also don't get the same sort of light dynamics with the kind of stage composition in Smash Bros compared with Mario Kart. Perhaps when we see more Smash in motion with regular gameplay, we'll have a better look at the big picture.

That's exactly what I was thinking. You read my mind.

Smash looks fantastic up close at 1080p, it has a shit ton of detail. you know 1080p is x2.5 720p of pixels right?

MK8 is done and about to be released and SSBU still has 6 months of work / refining to do... and it already looks really good.

Dat Jesus Camp gif.

But I actually like Brawl's style more, but this is growing on me. Who knows? Maybe once in play, I'll love the new one more.

What? Graphically? Nobody cares about that shit anymore. Smash is 60fps. It's graphics are clear and well defined, and the new gameplay changes look freaking incredible. That's all that matters to me.

The original Mario Kart was a graphical showcase on the SNES.

I keep hearing that Smash is 1080p but I haven't been able to find confirmation from Ninty. I can only find second hand articles that could be making the old mistaking-upscaled-for-native goof, haha.