i think there's also an app that looks for comparable apps for windows. like, you type in the app you used on iphone or android, and it will look for a comparable one on windows. i thought the apps were lacking, but i use a TON of apps. for many people, i think the selection would be fine. i also found some apps i preferred (i think they were actually nokia apps for windows) to the android ones, but overall they just didn't have enough for me.
As others have said ... it all depends! I found some of the Windows apps to be better, and others were very clunky attempts to emulate the Android apps. So it really depends on what apps you plan to use, or need to use, and how that translates to the Windows OS.
I will say that lots of places around town that advertize apps (retailers, banks, etc) state they are only available at the Apple sore, or Apple and Google Play. Windows and even BB seem to be lagging.
The number of apps on WP is increasing quickly. You can do an internet search on your favorite Android or iOS apps and find comparable apps for better than 80% of these apps on WP. Also Google is finally releasing APIs for Windows Phone developers to create apps that access Google Services like Gmail, YouTube, etc. This will make more of the "missing" or comparable apps that access those services available over the next several months. There are some pretty good third party replacement apps out there, sometimes even better than the official apps.
Apps are also being released from larger retailers, banks, and so forth, like The Home Depot for WP. As demand rises, smaller companies will opt to release WP apps.