I would say just about any Gottlieb Sys3 game I've owned since many of the modes are time based. Easy to understand and explain the rules/modes and just get to playing.
Wipeout - good luck completing Hot Doggin' to double your score - have to complete the drops and then the standups behind them and the shots are risky. Mogul event is tough to do in the time allotted too. Also want to make sure you don't start this mode until later in the game so you are trying to double 500 million instead of 500,000.
Rescue 911 - Simple rules, but again the modes are time based. Also have to set the Helicopter for manual ball release to make it tougher and more fun.
Big Hurt - actually I think I have this game down pat and may need to shorten up some mode timers. But what a fun and loaded game. A fun challenge is to go for high scores for catches, home runs, stolen bases, grand slams. Easy to understand and challenging to complete. I also like being able to play for high score or for most run. Going for runs is really fun with two players and it changes the strategy versus purely going for points. Also trying to complete the Billion orbit shots - haven't been able to do that yet or even get close.