It's more important, IMO, to ask what functionality is/isn't there than how many apps there are. There can be a billion and one apps, but if the one(s) you need isn't there, the hgih numbers don't help you much.
When I started with WP7.5 there was a lot missing. On WP8 there are a lot more, though still a few gaps (some filled in by similar apps). We are seeing a lot higher developer adoption, so I am betting we will start seeing Windows catch up here.
Also, as a side note, windows Phone doesn;t consider the trials as a second app, whereas iOS and Android do. So for things like games that often have a "lite" version, Android and iOS will count it as two apps where as WP just one.