If Warcraft & Starcraft had been the first games to use that naming convention, it actually would be pretty reasonable for Blizzard to claim that as a trademark.

Certainly, when I first encountered some other game called <genre>craft, I initially assumed it was a Blizzard title. Maybe that was dumb of me, but I had such a strong association between Blizzard and that type of name. That's exactly what trademarks are all about -- preventing customer confusion.