I haven't thought of this one. I know that most adaptions of Narnia have started with The Lion, The Witch, And The Wardrobe. I think if Netflix start with The Magician's Nephew, it could be a different take and it could make it stand out from the others. Besides, it's something we've never seen done on screen before. The only adaption of The Magician's Nephew we've had are from audio dramas, the BBC Radio 4 and Focus on the Family Radio Theatre. So I think Netflix could make a franchise stand out if they start with The Magician's Nephew on screen.

I personally would love to see them do "The Magician's Nephew" first, it's one of my top favorites from the series, and it's not been adapted before! There's just so many cool things I would love to see in visual format; The Wood Between the Worlds, the dead world of Charn, Jadis telling the children how it got in that state (a good opportunity as she's narrating to show it), the fight at the lamppost, and of course.... the creation of Narnia itself! I won't deny it's this book I am most excited about finally being adapted to the screen!

It would be different, yes. It would be the franchise that introduced answers to the questions posed by LWW, before the questions were asked.
How is that an improvement?  LWW would have lost a lot of mystery and excitement. I agree with decarus's post earlier (well stated, @decarus)

Even though my set of Narnia books has The Magician’s Nephew as number one I think it would be much better if the Netflix series starts with The Lion, the Witch, and the Wardrobe. The beginning of the story and the series works the best magic with Lucy Pevensie discovering the wardrobe. The effect of the magic of the stories may be diminished if something is put before the first few chapters of The Lion, the Witch, and the Wardrobe.  The wardrobe is essential in introducing people to Narnia, and that applies to all adaptations, including TV series.

I've said this before but if Netflix is smart, they'll adapt MN first.

1) Chronologically it's the first story in the series, and if they're going to be treating the book series as an overall cinematic/tv universe with spinoff potential, it makes sense to start there. 

2) It's the only book that could be adapted as a one-off, where you wouldn't be hampered by choosing specific actors that would have to come back or would have to be used as the basis for the younger actors when it comes time for them to be cast (like the Pevensies in HAHB). 

True, there's Aslan and Jadis, but both could be fairly easily recast. Voices for CGI characters get changed all the time, and Jadis' change of appearance could be handwaved away as her wicked magic affecting her visage. 

3) LWW is undoubtedly the most popular book in the series, in terms of general audiences at least. That's why it's important they don't adapt it first. I know this logic seems somewhat backwards but keep in mind, look at what happened with the Walden movies.

Because LWW made over $700 million as the first movie, every subsequent one seemed like a failure, even though PC and VOTDT actually had very consistent returns ($419 million and $415 million respectively). 

4) In addition to this, it also makes sense to adapt MN first as a kind of pilot and if the numbers aren't up to what Netflix are expecting they can not only reconfigure the elements of the show, but also bring out the big guns with LWW as the next adaptation.