I don't think any of the replies really have it. There are shades of grey in how the phrase is used, but:
Lowest Common Denominator does not merely mean mass market or casual. It implies a lack of ethics, a lack of artistic merit, appealing to baser instincts, it's condescending or patronising, there may some strong contempt for the target customer, undoubtedly an expectation of low intelligence and lack of education amongst the buyers or audience.
A product for the lowest common denominator is usually expected to be low quality, made on the cheap with the highest mark up possible and sold to morons, the gullible, and people who just don't know any better.
In TV land the endless make over shows, reality TV (like Jersey Shore) daytime talk shows (Springer, Kyle) would easily be described as appealing lowest common denominator. However, a show like American Idol might be described as both high quality mass market and lowest common denominator. Here the show straddles the grey area: it largely avoids being patronizing, it's respectful as the critiques don't insult the viewers intelligence. Yet in the early rounds of auditions there are clearly freak show elements that only exist to exploit and humiliate the participant.
Nintendo I think is an excellent example of how to misuse the phrase. Love or hate them, Nintendo games are consistently very high quality, broad appeal for sure, but always intelligent, well designed and never exploitative.
If you want to find examples of games that are for the lowest common denominator you need to consider games that are typically cheaply made and contain low quality gameplay, sold primarily based on graphical gimmicks, sexual exploitation or cashing in on the popularity of something else.