Walk into any shop and you'll be told, "This is the same as iPhone/iPad." Not only do customers walk out with an inferior product, but they think Apple's products areawful too. Apple's business is harmed and they should be able to sue over it.
The proof is simple. Show Samsung and HTC products before iPhone/iPad, then show them afterwards. And not just a picture of a screen with icons. Show the function of these devices, see how different they were and similar they are now.
It's easy to fall into the trap of thinking, "Well that's what a tablet should look like and work like, it's obvious." It wasn't obvious before, but it is now, now that Apple made a great product, for everyone to copy.

Apologies to slashgear.