International Soccer was one of if the the first major soccer game released for the C64 and the only game I ever had on cartridge as it came bundled with the system I bought. I don't know how common they were in the US but in the UK they, along with floppy discs were non existent as we used tapes to load games.
International Soccer was no frills in terms of sound, with generic crowd noises and the referees whistle and such. For an early game though, the graphics which don't look much in screenshots were absolutely beautiful and gave a very nice 3D effect. They were huge sprites, most other football games of the time were absolute dross which offered nothing like the gameplay this did.
The gameplay mechanics were actually really slow, to the extent it seemed your players were running in sand and the football took an age to reach the player you passed it too but this actually benefited the game making it a much more fun experience. Many soccer games that came afterwards were played at breakneck speed and if you were an average to poor gamer like myself you soon lost the ball and spent the game chasing it back!
There were actually no fouls awarded in this game so no penalty kicks either. Unrealistic but it worked as to get the ball back you had to time getting to the bounce of the ball.
There were no leagues involved it was just a one off match against the computer or a friend and bizarrely you were awarded a cup by a beautiful princess at the end of the game. At least that's what my 10 year old self though, perhaps it was just a woman!!
One fun memory of this game is that if you time it right you could head the ball in the air and bounce it on your head whilst running all the way to the goal. Stupid, but immensly satisfying as a kid!
This game was actually released by Commodore itself, and perhaps it was their best one too.