It's interesting that you say this in a vacuum, ignoring Samsung's changing their boxes, their power adapters, their USB cables, and even putting the phone with the app drawer exposed so it looks even closer to the iPhone on the boxes.
I'm absolutely not ignoring efforts but there is very little evidence that any of them were even trying to move in this direction outright - let alone with capacitive touch, glass over plastic, no keyboard, etc. Samsung's first attempts at this were actually Windows Mobile phones that launched after the iPhone 3G came along, and they were an absolute joke...they didn't function well at all, obviously they needed a lot more time and someone else to make the software. And that's exactly what led to their next iterations of copying the iPhone.
As for tablets in the 90's, my recollection is that they came along around 2003-2004.