In your view, which game developers have best retained their quality and record over a long period of time, and conversely, which have notably declined and become shadows of their former selves?

Name me a bad Dragon Quest mainline game. They're all great. 40 years as good as ever. Enix never dipped. 

Capcom was the first studio to pop into my head that have stood the test of time. They are doing better than ever, minus the reception of Monster Hunter Wilds.

dragon warriors 1 on nes wasnt that great

...Sure the most influential game in the genre and became the most popular franchise in Japan, wasn't great.....riiiight. I can say dumb wrong shit too. Check this out. Super Mario Bros or Zelda was not great.

Nintendo R&D/SPD/EAD/EPD,
It was first established by Gunpei Yokoi way back in the early 1970s, and grew into the most consistently powerful gaming studio in video game history. We’re looking at over a half a century now of existence, and first taking the top spot critically and commercially 40 years ago.

Really? I’d argue that Dragon Quest was one of the biggest and most well received releases of its time; enough to inspire multiple remakes and remasters.

Nintendo is still going strong. Rockstar never disappointed me. But they haven't released a new game in quite some time. Same as Naughty Dog. And that's about everything that comes to mind right now, lol.

On the other hand, we have Bethesda. I loved Morrowind and Fallout 3. I didn't even mind the bugs, because the games were fun. But ever since then, their games went downhill. I didn't even bother to try Starfield anymore.