@Maxotics,
As far as I'm concerned it's not your imagination, in fact,I think the D5300 looks better than the D800, but that's just to my eye. Although, I will say i've looked at the D800 for a long time as one of the best full frame cameras out there, but the price of it has always turned me away. Also, I've heard, and Andrew would definitely know more about this than I, but the word is with the 36MP sensor, you really need a good piece of glass to reap the resolution benefits from this camera.