why is henry always so nice to gold and not as much to regina when he said so himself that gold is worse then regina?

Simple. Henry is a badly written character. The writers have forgotten that Gold had recently threatened to kill the entire Charming family before the trip to New York, if something happened to Belle.

And this show is also sexist, which is why Henry seemed to have less trouble in his relationships with his grandfathers and his father, than he does with his mothers.

I think there's a couple of things going on here.

For starters, Henry hasn't seen Regina in quite a while. She was holed up in her vault for a few days (at least(, and Snow, Charming, and Emma didn't want Regina to see him before that. And now he's in New York, while Regina is back in Storybrooke. There's a lot of things working against Henry having any sort of contact with Regina that are making it look like Henry doesn't want to talk to her, which really isn't the case.

Next, I think Henry realized that Gold has a soft side. Gold risked a hell of a lot leaving Storybrooke just to find his son. Henry knew everything about what was going on: with Cora, with Belle, with people loosing their memories when they crossed the line. And he saw Gold choose to go after his son anyway (and we know that Henry is big on parents re-uniting with their children).
And Henry saw how out of his element Gold was the whole time. All of this, I think, humanized Gold in a way Henry didn't think possible, and made it a little easier to talk to him.

And, lastly, Henry just found out that Gold is his biological grandfather. Of course he's going to want to talk to him.

It's simple Henry is an eleven year old boy. Gold is the interesting unhinged grandparent that the rest of the family doesn't like to talk about. So naturally he wants to find out all about him, if only because his parents dont want him too. Regina is his mother and what preadolescent boy wants to be seen being all buddy-buddy with his mom exspesally when everyone in town hates her.

Because he's his grandpa?

Because this show absolutely loves every chance they get to send the message that adopted family doesn't count as actual family -.-

But Henry is just a kid. I feel like everyone has too high of expectations for him sometimes. He's only eleven. He doesn't have everything figured out like he thinks he does. He's going to to some stupid things.
(Plus, he's related to the charming's, so he's probably going to do some seriously stupid things.)

Regina and Henry haven't really spent some quality time these days. I actually like mr. Gold, and I personally think that a mother is a mother and sometimes talking to other people (not your mom) is easier.

For one, I think because Gold was always kind to Henry it made a difference. He let him use magic without paying for it. With Regina, it's a bit more personal for him because 1. He knew about the other world, and she made him feel crazy for it and 2. she's very controlling. It's more of a parent/child relationship, especially when said parent has made so many mistakes. He also understands Gold's plight with Bae/Neil because Henry went through wanting to know what happened to his biological mother and wanting to know more about her. The separation between parent and child is something he understands and with which he sympathizes.