I rarely use the phone camera. But I do transfer my Nikon DSLR library to the iPad and iPhone. Out in the sun, I agree, it doesn't matter. But indoors, there is no comparison. Samsung devices are not cheap at all, so there is no excuse using such crappy panels.
Which brings me back to, why?
You aren't going to notice much difference on a 4" screen unless you have a better quality phone side by side. Phone cameras are pretty mediocre so why people are using mobile phones as a primary means to look at high quality images I do not know.
I'd rather have a cheaper phone with a good screen than an expensive phone with a great one.
The iPad in particular is really great for looking at photos, because of its very high density display and very accurate colors. And iPhone 5 has almost as good display as iPad.