The VSmile by VTech is a great way to allow your kids to have video games if you think they are too young for XBox, PlayStation, or Nintendo.  It is educational and easy for young kids to play.  The controller has big buttons, and you can even switch the side the joystick is on.

The system and the games are not too expensive.  It uses batteries and cannot be plugged in so that adds a small amount to the expense, but it makes it easier to move it to different TVs in the house or take it in the car.