Is Chansey/Blissey the most consistent Pokemon in OU across all 9 generations?

There has never been a generation where both Chansey and Blissey have not been OU.

RBY: Chansey OU, Blissey N/A

GSC: Chansey UU, Blissey OU

ADV: Chansey UUBL, Blissey OU

DPP: Chansey UU, Blissey OU

BW: Chansey UUBL, Blissey OU

XY: Chansey OU, Blissey UU

SM: Chansey OU, Blissey UU

SS: Chansey UU, Blissey OU

SV: Chansey RU, Blissey OU

I know Pokemon like TTar are wildly considered to be one of the most consistently strong Pokemon, but would you consider Chansey/Blissey to be more consistent? I mean these two are literally the face of stall, I can't see both of them dying out unless stall gets eradicated completely by offensive powercreep.

I also put them together because it seems like whenever Blissey underperforms, it's because Chansey is a stronger option due to Eviolite like in Gen 6 and 7