The significance is MORE than just a 2nd Mobile game from Nintendo & its' emergence there. It's also a LARGER share of DIRECT-TO-NINTENDO REVENUES & it signals LICENSING expansion, diversification, & reinforces their COMMITTED ENTRY (finally) into MOBILE -- coming on the heels of the wildly successful record-setting mobile-game Pokemon GO!!
1) 100yr old PLUS Nintendo has HUNDREDS of beloved characters, & unlike Disney who enjoys a passive ~$40Byr (yes, "B" as in Forty-BILLION dollars per year) in passive licensing revenues, Nintendo has closely-held their beloved IP (Intellectual Property, characters, etc..) & over 4,000 patents. However, that is CHANGING. And "Super Mario Run" is just the start as they begin to leverage & MONETIZE their IP.
2) In 2015, NTDOY ALSO partnered with DeNA for 5 new mobile games due out by Spring 2017. Some WELL-KNOWN titles & NEW products are being prepared to market by the #1 Mobile Developer (by far) in Japan .... COMING SOON: https://en.wikipedia.org/wiki/DeNA
3) Japan OLYMPIC GAMES Mascot "Super Mario" will be met with the FORMAL OPENING of an entire NINTENDO Theme Park (ala Disney) which NTDOY has spent the last few years investing, developing, cultivating & carefully curating... &, it will be the FIRST-of-THREE theme parks set to debut whereby Nintendo will FURTHER PROMOTE & develop their IP: https://techcrunch.com/2016/12/12/super-nintendo-world-theme-park-at-universal-studios-to-open-in-japan-by-2020/