Google Maps could very well be the most highly used online map service, why would anything else be better? GMaps’ data is proprietary, you can use it but with some restrictions and software developers can not use its full potential for their own benefit.
OpenStreetMap is a world map done entirely from user’s submitted data. Similar to a wiki, you construct the map details by adding street names, information of buildings, commercial and government establishments, everything including terrain information.
The amount of data OpenStreetMap has about some areas in Europe I checked sometimes is even better than Google Maps. There are thousands of active participants throughout the world collaborating in this project. You can participate in various ways, from uploading data recorded by your GPS unit and even editing directly on the web in OSM’s own website.
With OSM we can have a project such as Open Route Service that provides a very nice set of directions to and from your next destination. If there is any information in these services that is incorrect, we can easily fix it.
The only thing I think would make it better is adding more user generated photos so we can have something similar to Google’s Street View.