This has to be a regional thing, similar to how in some areas of the American south, "Coke" is a generic term for all sodas. But at least in my area (Portland, OR), what you're saying is definitely not true.

I've never heard someone use Apple trademarks as generic terms. The generic term people use for a touchscreen smartphone is...a smartphone. Likewise, a generic term for a tablet is "tablet". I've never heard someone use "iPhone" to refer to all smartphones or "iPad" to refer to all tablets.

Though as a kid, I know my parents would say to "put away the Nintendo" when it was the PlayStation stuff that was all spread out on the floor.