Some nice, smooth, consistent quality. Better Call Saul was in my opinion pretty consistent. Single season anime is almost always consistent, like My Dress-Up Darling or Terror in Resonance.
Not dragging on longer than the series needs to seems to be a key point.
Fullmetal Alchemist: Brotherhood (haven't watched 2003), remember that being rather consistently good
Also Gravity Falls, but I haven't rewatched it since it ended in 2016 so I may be looking at it through rose-tinted lenses
Gravity Falls ends too early.