There are quite a few video games made in the past 20 years that weren't that popular and some that were wildly popular. It's interesting that some of these games - popular or not at the time - are now worth a bunch of money. One of the most expensive video games is "Birthday Mania" for the Atari 2600.
With only one verified copy in existence, "Birthday Mania" is one of the rarest games of all time. "Birthday Mania" allows players to play mini games consisting of popping balloons and blowing out candles. It also comes in a box that allows you to personalize it with a birthday message or name.