Mario & Sonic at the olympic games is an OK game. You might get bored though because you unlock events as you go, the more you play, the more events you unlock. An un-true cheat is if you play the circuit you unlock an event(s), I hadn't done a circuit and I unlocked all the events, though I suppose it takes longer that way.
This is for ages of when you are able to start playing video games to about 10-13 year olds.
If you like war games/guns you should try Halo (or possibly bioshock {which I don't know much about} Bioshock & Halo rated M (17+).
*not all events are same as olympic games.
