I feel like ranking every main SML character including characters who were a main character only for a brief time
Mario 7.8/10
Tony 5.2/10
Mama Luigi 7.5/10
Shrek 8.7/10
Black Yoshi 10/10
Bowser 8.5/10
Chef Pee Pee 9.6/10
Bowser Jr. 6.5/10
Joseph 5/10
Cody 8.4/10
BTG (8.7/10
Rosalina 4/10
Jeffy 5/10 (His appearances drastically differ in quality so his score is perfectly even)