Are Summon - [insert-creature-type-here] cards creatures?
Yes, these cards are MtG cards with the type Creature. A cards official wording is what currently appears in the Oracle Online reference.

From the Comprehensive Rules


  108.1. Use the Oracle card reference when determining a card’s wording. A card’s Oracle text can be found using the Gatherer card database at http://gatherer.wizards.com.





  Summon (Obsolete)
  Older creature cards were printed with “Summon [creature type]” on their type lines. All such cards have received errata in the Oracle card reference to say “Creature — [creature type].” (Many of these cards’ creature types have also been updated.) See Creature.