I don't think anyone is under any illusions about the quality of Urban Champion. My understanding was that Urban Champion only received the 3D Classics treatment because of the cache of nostalgia it still has in Japan (that, and the fact that relatively speaking it was probably quite easy to update given how little there is to the game). Nostalgia is a pretty crucial component when it comes to these updates and whether or not we find them worthwhile. I thought Kid Icarus, with it's new backgrounds, and Excitebike, with it's ear piercing music, were great updates, but then again I already had a certain amount of affection for both those games.
I just hope that Nintendo eventually make a Metroid 3D Classic. Although I did enjoy Kid Icarus (NES), I actually never got very far in the game. It was only with the 3D Classics version that I was able to make any significant progress, and I really enjoyed it. So my hope has always been that '3D Classics' would give me the opportunity to potentially enjoy some of the classic games that, while much lauded, feel archaic to me. Kid Icarus was definitely one of those games, and (I'm sorry to say) the original Metroid is another.
My hope would be that if Nintendo ever did decide to update Metroid for the 3DS, they would make a few slight refinements and alterations much like they did with Kid Icarus. New backgrounds for instance would do a great deal to help me differentiate between areas. Perhaps some health stations could also be added, so that I don't have to farm enemies. Simple things like that would go a long way towards making that game more enjoyable for me, without detracting from what people enjoy about it; and who knows? Perhaps I might actually finish it for once.