There is no way of telling which Sanrio character is the best, as it all depends on each person's individual preferences. Each creation has a different back story to love, but Hello Kitty does seem to be the most popular character amongst young people.
Below is a description of each of the five characters that you asked about in your question. From this you can decide which one you believe is the best.
Hello Kitty is Sanrio's most popular character, although her real name is Kitty White. She is a white female Japanese bobtail cat with a red bow on her left ear, and has become an icon in Japanese popular culture. Kitty was born in London on November 1. Her weight is "three apples" and her height is "two apples". Her favorite subjects at school are English, Music and Art and she loves to make cookies and apple pie.
Chococat is a black cat with big black eyes, four whiskers and has no mouth. He was born on May 10. He was originally depicted to be wearing a blue collar but the color tends to change. Some Sanrio products show Chococat as grey-brown in color. In Momoberry, Chococat is pink with a bow tie, cane and top hat.
This character was born in 2002 on March 6, and is depicted as a white puppy with very long ears that allow him to take flight. His eyes are blue and his tail is curly and plump and looks like a cinnamon roll, which is where his name is derived from.
This character is portrayed as a female rabbit who wears a pink or red hood that covers her ears, taking inspiration from Little Red Riding Hood. She was born on January 18. Although the My Melody character has experienced increased popularity with women of all ages, she is still yet to reach the global popularity of Hello Kitty.
This Sanrio character is pictured as a frog that has a large V-shaped mouth and large eyes and he has a very bubbly personality. He loves to have adventures with his brother Koroppi and sister Pikki. He also likes to sing and swim in his home town of Donut Pond.
