Agreed, though I suppose if the games do take advantage of the iPhone itself being a controller then that could help set a difference between $5 & $10 games. Though you can still end up with some very average games.
We are in agreement, but I also think the games need to do more than just us the iPhone as a controller. The DS I think is the near perfect model. They basically have 2 tiers games $20 brain age type stuff and $30 more in depth games. As far as the iPhone goes the monkey ball game demoed with the reported '100s' of levels is probably worth $10. A remake of Zuma? Not so much. Bring something like a Final Fantasy RPG to the iPhone and I'll be the first to pay $30 for it. I'm worried that now that the starting price for games seems to have been set a $10 is that that is now the floor. At $10, I personally won't just grab something to try it out as I would at $5.