I've only played the online versions, haven't downloaded the games.
Good time waster, quite a lot of fun.
The radar one is fairly realistic, the a/c seem a little slower to take up turns than in real life, to me. Available tools for the game are a little limited compared to real life, but within the context of what is there, it's pretty good.
The tower based games are more limited in terms of tools available, the separations we are required to use are not depicted on the game, thus unrealistic, you don't tend to get a/c following each other down final so close together that routine overshoots are required, and in the game it is depicted that if you send one around it might crash into another one a couple of minutes later, outside your jurisdiction, which is highly unrealistic. Also unrealistic is the weather complexity. You can't control an aerodrome that you can't see without either position reports or radar.
But all in all, a lot of fun.