Yeah, Ultimate Spider-Man is childish and lame. I can't even bear to watch that show after watching the first whole season. It's pace for story is slow, and the filler is mostly jokes and sad action, only using stupid villains like The Trapster (which is originally known as Paste Pot Pete) and Batroc on a regular basis.
And when they use a major villain, it's not always Spider-Man's. They were more eager to show villains like The Frightful Four or Taskmaster. Whether this was for them to distract us while the Green Goblin was built up, I don't know. But if they want to grab the attention of younger kids, show how awesome you can make the classic villains!
Their portrayals of Doc Ock, Electro, Lizard, and even Green Goblin really are downsized to how Spectacular Spider-man did them. They feel like they're forced to act evil in Ultimate, but in Spectacular, it makes them feel that every thread of their inner being is evil.
Oh, and I hate the re-imaginings of most of the villains, too. primarily Goblin, Doc Ock, and Venom. Lizard was okay.