Wellll, the reason why Mother is on the F Tier because it pretty **** as a game. The atmosphere is pretty great, but as a game? It's pretty terrible. Melee is overrated so bleh. Finally, K Rool is a furry.
D, C, B, and A is literally self explanatory.
Brawl is easy the best game in the whole series; it's literally perfect. People are just mad about it because of "oh it ain't competitive!!!". Splatoon is the only real good Nintendo IP nowadays, and I think it's pretty clever to hold off content of the game for longevity. I added Dark Pit on the list because he's my favorite character to play as.