On the 909/303, I don't dispute they were incredibly influential in the rave scene, especially in the 90s. I am one of those people with a 303 tattoo so I know very well what a reputation they had. But also I have some perspective on how small and dynamic that scene turned out to be in the greater scheme of things. Most of the ravers I know from back in the day couldn't pick a 303 in a song and don't even listen to acid or techno music any more.
I think a good comparison to an 808 is a Theremin. Lots of people, even people who don't listen to electronic music or hip-hop know the names of these instruments and can probably pick one out of a song. I'd see the 909 or 303 more like a Strat or a Tele - still very influential and recognizable to people who are interested, but perhaps not so much in the mainstream consciousness.
But this is all opinion just based on anecdotes, so I am open to the idea I might be overestimating the cultural impact of one bit of gear or the other.
About 909s and 303s, like I said, they were special when they were in their heyday. Most people knew them by name, since there were lots of track titles, there was a TB-303 reference in Ghost in the Shell, and there are some TR-909 and TB-303 tattoos if you search Google... I'm not disputing that 808s are more famous now that hip hop is very mainstream, the 808 kick drum is in vogue for years and Kanye albums have 808s in their title. Like I said, you have to keep those things into context when making a comparison, otherwise only the 808 will ever count as "important"... that's it. Maybe the Moog is a better example?