Train. The railway network covers all of France. If you travel between major cities using  the high speed train, you can travel faster across France by train than by plane if you consider the total travel time. It train network is reliable and trains are on time or reach their destination with only minor delays.

Car - There a lot of well laid out and maintained roads, a network of motorways and secondary roads. However, the toll roads (motorways) and high petrol prices make a long trip very expensive  for a traveler .

Plane - There us one main airline, Air France. There are also many airlines that offer cheap tickets but you have to go to deserted airports in remote locations sometimes to catch a flight. However, it can be the best option if you do a cross section travel across France.

Coaches - There are some coaches running between cities , but generally train is better.

For transport of heavy loads and cargo you can choose between trucks, train, plane, and waterways. The well developed canal system allows barges carrying cargo to go from one river to the other.

All the big cities of France have a large network of buses, and for the major cities have underground railway system. The most advanced railway system is in Paris where a railway station is a five minutes walk away from any point in most of Paris.