It's going to be a toughy. For me, I think the following will show promise:
SMS: if they managed to get GOW looking that good at that scale last gen, then this gen they should be able to blow us away even more.
Insomniac: Rift Apart showed us destruction, RT, partial effects and a ton more along with loading levels and world's and environments super fast. Additionally, the character models looked amazing from the fur right down to reflections in eyes etc.
GG: they managed to pull out KZ:SF right at th start of the gen and Horizon was a marvel with those robots which had some many moving and destructible bits. Their new game already looks amazing and this is with the game being cross gen.
Ryu Ga Gotoku: Kamorucho is one of the most alive cities I have come across in a game. It feels like every gen they make it come more and more to life along with greater detailed assets and models. GTA and Red Dead pale in comparison to Kamorucho.
Capcom: DMC, Monster Hunter World and RE8 all looked amazing. Capcom can surely push the boundaries even further.
ND: here comes the big controversy. TLOU2 graphics impressed me more than the Matrix demo. The Matrix demo blew my mind, but when the dust settled I was left with more questions.
Everything was static. The trees, lamp posts, bins couldnt be damaged. Bottles on the floor comment be moved. Buildings couldn't be damaged. A lot of textures were muddy (dirt, mud, leaves, certain glass like material, stone NPC's).
Other than the number of cars and pedestrians, the city felt dead. TLOU2, was densely populated, felt alive, had more interactive elements, textures were better and had more unique assets. The Matrix demo was the definition of bigger is better, but lacked soul.
If ND could impress me so much with TLOU2, a game made last gen can compete with a specially made tech demo, then what they could do for this gen will surely blow our minds.
IOI: hitman games have always looked amazing. Each level crafted with unique assets and locations. Small details everywhere, a bunch of NPCs with their own AI and purpose.
Playground Games: FH is a marvel and if they can do this for an open world racing game that has to move so quick and, then with Fable they should be able to do even better.
The Coalition: Gears has always pushed graphics so it won't come to any surprise if the next game they make will push the benchmark even further.
Kojima Studio: what they did with the decima engine and Death Stranding was amazing. Again this was done on last gen tech. How much further they could take things this gen surely will blow our minds.
Devs I've not listed:
PD: they probably won't release another game until the end of this gen.
NT: similar to Quantic dream, Hellblade looks good, bit probably achieves this through limitations in gameplay and level design. The last game felt very narrow where most things were covered in darkness. You can then concentrate on what is visible to push those effects and polygons. Forza Horizon, Gears, there is detail everywhere.
Ghost of Tsushima was beautiful and amazing, but mostly it was about the artistic approach. Most of what we saw was blades of grass, trees, fields of sorts. Probably one of the reasons it was able to load very quick and do what it did so well.
Housemarque: Returnal similarly to Hellblade pulled of great graphics and effects by limiting the environment and what you can see.
Ubisoft, Activision, EA: mostly they push generic annual games. With exceptions such as Jedi Fallen Knight, Battlefront / Squadrons, not sure if we will see any of these lot push boundaries. Ubisoft is in a similar place to GTA where it's about bigger maps rather than better maps. Activision just pushes COD and Crash isn't exactly ground breaking.
Anything Nintendo: Nintendo is about art style more than pushing graphics.
Devs that could but night go under the radar:
Atlus: persona games are amazing and I can see them doing amazing stuff.
From: Bloodborne and DS3 looked amazing, Sekiro not so much. Elden ring looks great, but I expected more in its looks for next gen, and From isn't really known to push graphical boundaries as much as art style.
Blue Point: they have done amazing work with the remakes, but i think it all depends on whether they have been given a budget to do a remake, a small new IP or a full budget for their own game. Depending on what they have got, we could see something spectacular.