[IceFire]

I know it wasn't mentioned specifically.... but flightsim?  IL-2 Sturmovik series is the best of the best and it's relatively accessible for a flight sim as you can turn on and off the features as you want to.  It fits your categories for deep gameplay because it will take quite a while to learn everything you need to know and when you've done that there is always more (fighter, dive bombing, level bombing and level bombsight operation, tank busting, etc.).  Multiplayer is easily thousands of hours are potential fun and offline there are hundreds of user created campaigns spanning pretty much all of WWII that you can play.  Also this is the sort of game a 7 year old could watch and not be concerned about permanent damage - except maybe a long term desire to fly and visit airplane museums (Aces of the Pacific from Dynamix did that to me ).

[Thaeris]

I'll recommend this one as well. I'd buy it from GOG, but there seems to be some pretty bizzare complications in doing that from my bank/debit card.

Campaigns are a lot of fun. Different every time, and always good fun. And, there's the fun part about getting to fly the P-40... 

[Vidmaster]

I actually can't. I just like a well told story.

[Marcov]

If you want a good, exciting, and dramatic Flight Simulation (aside from FS) get Red Baron 3D. A relatively old game, but the mods make it.

Though there are several bugs, I really ignore them and look foward to dogfighting aces. You can start a career as a pilot, first pick your side (British, French, or German, and American in 1918), pick your squadron, and pick the date you want to enlist in (the date affects the type of plane and the season in which you first participate; for example, if you enlist in December 1915, then you'd play the first missions in Winter, and you get an early aircraft; e.g. Fokker Eindecker).

If you get more than 5 kills, you're usually allowed to paint your own plane. You can also be allowed to paint if you're a high-ranking officer.

If you get of kills in a single mission, you get a medal. The number of kills you get affects the rank of medal (for example, if you got 2 kills you'll earn an Iron Cross, 2nd class; if you get like 4 kills, you'll get an Iron cross, 1st class; if you get 9 or 10 kills you'll probably get a Blue Max/Pour le merite or something).

What I really like here is confronting the aces themselves; its simply dramatic 

Once I got an uber 100 kills (above the Red Baron) but only because I cheated  .

However, when I get killed I usually "abort" the mission instead of "ending" the mission (aborting won't save the mission's status; ending will) so my career won't end. 

[Thaeris]

No storyline, but you could always get X-Plane. Then you can build your own plane and make your own adventures... 

Also, don't be afraid to browse through Abandonia.com. You might find something there...