I think interest is at an all time high, with everyone who grew up with NES, SNES, etc, reaching that age where they want to buy all their old games back, and honestly the modern game industry is a bit tiring, turning a lot of people back to the good old days.
SNES prices seem particularly outrageous, I think.. Seems worse than NES in my opinion, but I haven't been in the scene long. Before this, I was in Japan hunting down Famicom games.
But anyway, I think there's a bubble that will burst on a lot of games that aren't as rare or valuable as people want you to believe.. Meanwhile, the rarest games may stay just as rare and may increase in price.. But the run of the mill stuff is priced waaayy too high right now.