Let's get a little discussion going here... I know it's an old premise, but let's say for the heck of it you're on a deserted island with an Intellivision and three - or maybe to make it easier, five - games. What are they?
I'm somewhat new to the Intellivision, so I may overlook a popular title that I just haven't experienced, but here's my list:
1) Astrosmash. I was raised on Atari, and had the M Network equivalent, Astroblast. Looooved this game. I'd have to choose it because It's easy to pick up and play and is just as much fun for a five minute session as it is to see just how long you can play before losing.
2) Thunder Castle. I'm not sure what it is about this game- it's not so action-packed or anything- but I love it. To me it's an underrated maze game with great music. The only thing that might have kept this off my list is I can only make it through the first two screens, but I figure if I were trapped on an island, I'd have plenty of time to improve.
3) Snafu. I know, I know... for all of the involved, technical, complex games for the Intellivison, why choose Snafu? Love the music, and for a simple game it somehow stays fresh. The music is going through my head as I type this.
4) Donkey Kong (2011). I can't give all of my love to only the releases from back in the day. To me, this game is a huge technical achievement, and despite it's shortcomings, I can still call it a favorite. I was obsessed with Colecovision Donkey Kong as a kid, and that's a factor as well.
5) MLB Baseball. It was the sports games that really set the standard for excellence for the Intellivision. I remember hating George Plimpton as a kid during thoise commercials comparing Atari 2600 to Intellivision. I was a fanboy of the 2600 the way there are Xbox and PS fans today, but I could not deny the greatness of baseball, football, etc. compared to their Atari counterparts. (For this selection, I'm assuming I'd have one person play or another player.)
Honorable mentions: Burgertime and Shark Shark