As someone who loves playing Genji.....I hate Mei. Now that I think about it, it's funny.
When I first started out, I was so hilariously bad with Genji, I was jokingly thinking things like "yeah this is my main offense hero right here". Overtime after playing him as a joke with some friends, I ended up really liking him. So now he's just my got offense hero. my go to for other roles are Junkrat/Bastion on defense, Reinhardt/D.Va on tank, and Lucio on healer.