This has been a common complaint with G4.0 (as well as G3.5). Some of the earlier versions of RealFlight had much better physics, such as G2 and G3.0, but for reasons known only to the developers they made the planes fly "easier" when G3.5 was released to the public.

In the newest version, G4.5, they've returned to much more realistic physics. The problem is that you have to set them yourself.

From the Help file Under "Difficulty":

Difficulty
One of the great benefits of RealFlight G4.5 is the ability to adjust features and settings
that you would not be able to at a real flying field. The Difficulty setting is one of these
great features. It allows you to adjust how realistic the flight physics is in the simulator
on a global scale, meaning that all of the simulator’s characteristics reflect this
modification. The options that are available are as follows:
Beginner-
This setting is perfect for the first time pilot. It reduces the speed of the
physics to allow a beginner time to react and learn how an aircraft is controlled.
At this level, you cannot run out of fuel and crashes are more forgiving.
Intermediate-
By default, RealFlight G4.5 is set to Intermediate. This level is the most
realistic to real life flying. (this is the opinion of the developers and is not shared by a great many users)
Advanced-
The flight physics level for Advanced is very similar to Intermediate. But you
will also notice that the severity of the stalls have also increased, forcing the
pilot to react faster to stalls and other similar flight characteristics.
Custom-
This menu option is grayed out as it can not be selected directly. If you wish
to adjust the different parameters of the flight physics individually, this menu
item will be checked. See the section Settings on Page 77 for more details