The key to a great game is replayability, so when you can play a demo of a game with the same teams, with only one half of a match over and over and over and over, well you get the point, it shows that it's a good game.
This was the case for me and ISS PRO 98. I couldn't find the game anywhere to buy for ages so I played the demo repeatedly, being Brazil vs France. When I finally got the full game I won the World Cup with most if not all of the 32 countries.
This game showed me how good soccer could be with a controller and I never looked at a FIFA game the same way after this. It also got me more into the sport of soccer which I am very thankful for.
For its time this was the best sports game ever and is still fun to play today and after playing 'ISS Pro' years later, this was a sizeable jump forward in gameplay.