Risk was a great board game, which for some reason didn't translate well into a computer game. Maybe its lure was more about the personal interaction between opponents than formulating a strategy for conquering the world.
In any event, besides being fun, hours of Risk also embeded obscure geographical facts learned from hours of battle. For example holding Kamchatka was damn near impossible - it could be invaded from FIVE different locations! Try defending that piece of territory! (and thinking of this always reminds me of the Princess Bride quote about never getting involved in a land war in Asia).
Australia and Indonesia, on the other hand, were the best defensive positions on the map. You could put all your armies in Indonesia, which could only be invaded from a single spot, and just put token holding armies over the rest of Australia. So Indonesia was the site of many, many of my last stands, but I made my opponents pay.
Greenland was also very important as it was the only way to get across the Atlantic. So you had to take it eventually. Its Risk importance, and my musing here was brought up by this Tigerhawk blog link:
With such massive potential oil reserves, Greenland is poised to achieve a geopolitical importance it hasn’t had since the invention of Risk.
Apparently over the years the map was changed and updated from what was around when I was a kid, plus no one plays this any more, so this particular way of learning geography is lost.