The "ui" elements are not styled after Lightning. If you want a Lightning style, you'd use "lightning" elements. In this case, it looks like you want the lightning:radioGroup to implement the desired look and feel. Note that you no longer have to create a bunch of radio elements, simply setting the "options" attribute with the desired values is sufficient.

Example From Documentation

<aura:component>
    <aura:attribute name="options" type="List" default="[
    {'label': 'apples', 'value': 'option1'},
    {'label': 'oranges', 'value': 'option2'}
    ]"/>
    <aura:attribute name="value" type="String" default="option1"/>
    <lightning:radioGroup 
        aura:id="mygroup"
        name="radioButtonGroup"
        label="Radio Button Group"
        options="{! v.options }"
        value="{! v.value }"
        onchange="{! c.handleChange }"
        required="true" />
</aura:component>

you need to use aura:html to create a html tag dynamically using $A.createComponent.

So to create a button tag below is how you do it:

$A.createComponent(
    "aura:html",
    {
        "tag":"button",
        "body":"click me",
        "HTMLAttributes":{
            "id":"dynamicbtn",
            "class":"slds-button slds-button--brand"
        }
    },
    function(newBtn){
        if (cmp.isValid()) {
            var body = cmp.get("v.body");
            body.push(newBtn);
            cmp.set("v.body", cmp);
        }
    }
);