The tier list is created based on the tournament performance of each character. It's not based on priority of moves or character speed or anything of that nature. If you study the tier list though, you'll discover that certain 'traits' tend to hold true throughout the list..
In summary, don't pick a character to main just because they are high on this list. Pick somebody you are comfortable playing to learn tech skill and game components in general, then you'll start to figure out which character's better suit your play style and you'll pick them. There is a high tier character out there for everybody, but you don't have to start there.