15 years ago, a "game console" (home or portable) was mostly something upper-middle-class children ownedNo. Unless you're talking about a country other than the US, this is absolutely incorrect.
Original Playstation sold more than 40,000,000 units in the U.S., and in the same console generation N64 sold another 20,000,000. On the portable front, the original Gameboy & Color version, beginning in 1989, sold more than 40,000,000 units. Keep in mind, there were only about 80,000,000 households.
There are not 40,000,000 upper-middle class households in the US. For reference, the original gameboy cost $90, roughly $180 in today's money. This is not out of reach for even poorer households. In today's dollars, even if you draw the "upper middle" line relatively low at about $100k for a family of 3, there's only about 30 million households at that level, and 16 million of them don't even have kids.
I'm not debating that video games have become even more popular in recent years, but they were mainstream long before that. "Mainstream" doesn't mean "everyone". The simple wiktionary definition is simply "Used or accepted broadly rather than by small portions of a population or market." I'd be hard pressed to say that millions upon millions of console owners isn't "used broadly".