Overwatch is a very fluid game. Any Tier List, these included, should be tempered with your own playstyle.
These lists are meant to give you advice and guide you in the right direction, but no list can integrate your own skill level and playstyle.
At the end of the day, play what you play best and not only will you be happier, but you will see much more success.
Good luck and have fun!
Heroes listed by offensive capabilities.
Heroes listed by defensive capabilities.
Heroes listed by tanking capabilities.
Heroes listed by support capabilities.