It's been nothing but regression since then.
Mega Man 8 had:
-Big, colorful sprites
-Fantastic animations
-Voice acting (good in Japan, so bad it's good in the west)
-A really chill soundtrack
-Great character portraits
-An extra focus on story without going overboard or focusing on it outright
-Hints towards the X series (REALLY subtle hints with the evil energy Wily found - again, not front and center but there)
-Anime cutscenes
I just feel like graphically, and stylistically in general, Mega Man 8 had the right idea. I think other games in the series play better, but 8 still has the most swagger in its step.
Mega Man and Bass was incredibly impressive for re-using its assets on the Super Famicom, but it was still a step back regardless.
Mega Man 9 and 10 went for the nostalgia grab, and scaled back on detailed sprites, extra story, character portraits, etc.
Mega Man 11 is a step back in the right direction, but its psuedo 3D isn't quite as charming as 8's spritework, its story is a bit lackluster, and its soundtrack is a bit underwhelming.
I know Mega Man 8 is a black sheep, and not very well liked by many Classic fans, but it's still one of my favorite games in the series, and felt like a major step in a good direction - one that's been backpedaled on since.