An iphone4 has almost the same screen definition as an HD TV
Oh nonsense. I hope you're not designing sites I ever want to view on my TV or desktop.
The iPhone 4 is 960 x 640 px, FullHD is 1920 x 1080 px.
Even with increasing resolutions of mobile devices, they're restricted by physical size. The angle of view of decent sized home based screens will always be far larger, mandating different design decisions.