I wouldnt go with the windows phone. Something about the OS that just lacks fun :O
Not sure how to explain it, i mean it's a solid OS and all but i was thoroughly underwhelmed by the lumia 900. The 920 might be better but the OS is still the same.
I guess that would leave the iPhone and S4. And at this point in time i think Android has the advantage. Apple are only starting to implement features that have been in android for a long time now...this wasnt always the case. The S4 is a really solid phone and the best android phone on the market.
I personally went for the HTC One...great phone. But I think if you looking for a well balanced all round great phone go with the S4. The HTC One and other android top end phones all have certain quirks that you may or may not like.