Posting this again..
1) Marketing
Dammit, I have never remembered seeing any windows phone commercial here in Singapore. Replace the whole marketing team. A product is only as good as the marketing. I'm talking TV commercials, billboards, sponsorship.
2) Apps
Now this is an arduous task but the all gap is still there, especially on the games front. I've seen many popular apps on windows phone this couple of years but they are seldom updated as compared to their iOS/Android counterparts. Maybe Microsoft could reward the devs if their apps get 500 000 downloads or something. Or if they have a perfect 5 star rating.
3) Customization
When Windows Phone was first conceived, Microsoft took the Apple approach but it obviously did not work out for them and we can see Microsoft slowly trying to become more like Android. That's a good thing. Android is popular for a reason, one of which, is it's customization. I'm not saying they should open-source windows phone but make it more customizable. Allow users to set default app for the web browser, keyboard, calendar, camera etc.
4) Hardware availability
Windows Phone now has more than 15 hardware partners. From HTC to Micromax. Nokia to BLU. But here's the thing. Alot of this devices are not available internationally. In the US, the Lumia Icon was only available on Verizon. The Lumia 930 wasn't released there. The HTC One M8, I believe was also a timed exclusive on T-Mobile (or was it AT&T?) In Singapore, the o ly windows phone devices we have is from Nokia. How could you expect your devices to sell and your OS to gain recognition if the hardware availability is limited. Microsoft needs to bring more devices to the market.
These 4 points, in my humble opinion, is crucial for Microsoft to take into consideration if they want to succeed and gain at least 15% market share worldwide.