To me, map data means just the data required to know what is where. I wouldn't count "satellite" images, geocoding, street view or anything like that as map data, but their own, distinct things. As it stands, OSM is one of the big 3 in that field, together with Google and Microsoft. Both of the latter might be as good when it comes to streets and buildings, but OSM destroys them when you also include hiking/bike trails, naval marking, traffic lights, power lines, etc. - some of which the other two don't provide at all.
Not to mention that afaik the "map data" itself isn't actually available from either MS or Google - they only sell usage of it through their limited APIs.
It's not quite like that. The three main commercial providers which have their own data are Google, TomTom and HERE(which Microsoft uses). TomTom and HERE would be more than happy to sell it to you for a fee - it's their main source of revenue.
The data TomTom and HERE have is focused on navigation use cases - it doesn't have so much 'visual' stuff as OSM but has has large quantities of information that is only relevant for car navigation, e.g. historical traffic patterns and lane assignments.
Huh, I thought I remembered something about Microsoft buying HERE. Glad to hear that's not the case. I did also completely forget about TomTom - last time I used their stuff was on a Palm Tungsten T3... Amazing that they are still around!
Not to mention that afaik the "map data" itself isn't actually available from either MS or Google - they only sell usage of it through their limited APIs.