This is a hard one. Emma gave him up, but she felt she had to, and she's redeemed herself since then, and genuinely loves and cares for him. Regina raised him, even though she wasn't very loving towards him for a time, but again, she's improved a lot. So I think they both have equal right to be called 'mum'.

As a parent it's your job to do whatever is right for your child(ren). To protect and love them without hesitation. Emma and Regina have both done that.

This is getting old.... To be honest i don't care....

Henry has two moms! Deal with it!

Obviously this is completely subjective since both moms really love him and care for him. Biologically he is really Emma's but legally he is really Regina's since he is still a minor and Emma gave up parental guardianship when she put Henry up for adoption. Also, Emma was never coming back to find Henry; Henry found her so I still consider Regina to be the primary parent if I have to choose.

Both of them but I will always be more protective over Regina/Henry's relationship because she's the woman who raised him all those years and never gave up on him. I'm not even sure Emma would want to contact her son if Henry hadn't found her in the pilot.
But after everything that has happened it's obvious that he has both moms that love him unconditionally!

Such an age old debate.

But yeah if I had to choose I'm with laylastepford.