You can't be serious - or, you have serious vision problems.
The difference between the iPad2 and 3 screens is night and day (for anyone with decent eyesight). There is simply no comparison.
This, however, doesn't mean the elevated dpi of the Samsung tabs would be useful - the dpi of the Retina iPads is sufficient. As I've pointed out above, it's not because of the higher dpi that Samsung screens are vastly superior to at least the Retina Mini screens (but not the Air / iPad3/4 ones): color gamut. In which rMini's suck really hard.
We went from two iPad1 to two iPad4.
The difference in display/pixel resolution is minuscule using them at a normal viewing distance of about 10-12".
We leave our iPad's out for guests/friends to use all the time and when we switched from the iPad1 to iPad4, no one has even mentioned anything about how much better the screen looks viewing pictures, video's or the web.
Retina is probably only useful for those who use their iPad's at 6" or less and like to get retina burn.
Most people who mention retina display do it for bragging rights, which is sad.