Revisiting Wesnoth

I may have recommended it before, but Wesnoth offers as good a gaming experience as you can ask for, including...

• Simple, intuitive gameplay
  
• Great variety in unit types and settings
• Panzer General-like gameplay, but omitting European genocide
  
• 16 well-designed, de-bugged campaigns, each with a good story line and unique challenges
• Many other campaigns, some very good, available for download
• Most campaigns offer several different ways to win, lots of replay potential
  
• Pretty good soundtrack
  

And it's free.