I can't think of many. Even the ones who make great games still... none of them are making the sort of ground-breaking, mind-blowing games that they did in the 80's, 90's or early 00's. Yeah, they're still making great games, but the whole re-shaping-the-wheel thing is gone.

stayed great:

• Atlus
• Capcom
• Nintendo
• From Software

These are all japanese companies. Maybe there is something in the japanese company culture, or maybe it is the western culture of growth at all costs which makes studios lose their greatness. I don't know.

fallen off:

• Bioware (but Larian stepped in)
• Blizzard
• Ubisoft

Here I also see that many studios aren't around anymore. New World Computing, Sierra Entertainment, Interplay, Black Isle are all gone.

IIRC they were making more money than ever with their pachinkos, so if anything, people didn't really expect them to pivot back to single-player games.

Yeah that and the whole obsession with games having to appeal to "everyone" which generally results in homogenised mush.

Yeah, the appeal to everyone is more like "offend no one". But only because it isn't bad, doesn't mean it is exciting. And for games to be successful they have to be exciting. Which also often means that they might ruffle some feathers.

Exactly, Western AAA are almost never daring or edgy or sexy or creative any more because they're scaring of turning off tourists. They feel so focus tested and designed by committee that there's rarely any spark or style to them.

It's pretty incredible Tose is still around and always doing good work. They are almost 50 years old. They have developed original games. Ported games over the decades. Remade games. Some of you probably never heard of them but they are still going Strong. Falcom is another who has always made good to great RPGs. Ys. Dragon Slayer. Xanadu. Trails of series.

Success is another good one. Maybe most well known for their Cotton series but also done other shmups.Including a game on Dreamcast I love, Psyvariar 2. Games in other genres. Touch Detective. Umihara Kawase series.

Id Software. Do I need to say more?

Declined?
Compile. Now known as Compile Heart. Compile did some great 16-bit era shooters and of course the ever awesome MUSHA on SEGA Genesis. The other Aleste games. Blazing Lazers on TG16! Zanac. A number of the Puyo Puyo games. They were amazing! Now what do they make? Gooner trash for body pillow lovers. Esp that trash Neptunia series.

Yeah id is a great example; Doom is still as great now as it was in 1993 which is no mean feat, maintaining such a level of quality for over 30 years.

Insomniac Games

Other than the very generic Fuse I can't think of a bad game from them.

Ratchet was the PS2 mascot platformer who survived.

While they're not as old as some others here, Vanillaware have been around for almost a quarter of a century now and their stuff still rocks.