You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allredirects garcontinue="Cinnabar_Tunnel" />
  </query-continue>
  <query>
    <pages>
      <page pageid="295" ns="0" title="Base Experience" />
      <page pageid="2363" ns="0" title="Blackthorn City" />
      <page pageid="3543" ns="0" title="Bug (type)" />
      <page pageid="3002" ns="0" title="Burned Tower" />
      <page pageid="133" ns="0" title="Catchable Pokémon" />
      <page pageid="2486" ns="0" title="Celadon City" />
      <page pageid="1561" ns="0" title="Cerulean Cave" />
      <page pageid="1440" ns="0" title="Cerulean City" />
      <page pageid="2550" ns="0" title="Checking Pokemon IVs" />
      <page pageid="2382" ns="0" title="Cianwood City" />
    </pages>
  </query>
</api>