I think this is a funny question because I don't really think you are a mother until after your children are born. You learn everything about being a mother after they are born and you get to experience motherhood.
Before I was a mom, I was really great with kids. I loved being around them and loved watching them, but it is TOTALLY different after you have kids. You can't give your kids back when you have them and it is YOU being the one that is responsible for them.
So, I think I am a better mother now... because before I just had great qualities that would make a good mom. Now I know what my great qualities are and what ones I need to work on...
Being a parent is the most rewarding thing I have EVER done!