Do we perceive there are fewer geniuses nowadays?

My gut says there are fewer geniuses nowadays, although I don't really trust it on this one.

As for guts that aren't mine...Bruce G. Charlton. Gideon Rachman. Dean Keith Simonton, although he simultaneously argues that modern first-rate scientists, "[i]f anything", need "more raw brains". Cosma Shalizi, who I think is being serious there, not just florid.

I think we tend to pick the one thing somebody did in each generation or decade that seems most impressive, and call whoever did it an Einstein, with no idea how hard or easy it really was.

I think there are certainly people who do that. There are people (not sure I can name any, but I'm sure they exist...Ray Kurzweil, maybe?) who are relentlessly upbeat about the march of scientific genius & progress, and people who just like jumping on hype bandwagons. There are also people with gloomier outlooks.

Today, we've got genuine genius entrepreneurs like Sergei & Larry, Peter Thiel, and Elon Musk, yet the public thinks the great genius of that generation was Steve Jobs. Possibly because Apple spent many (dozen? hundred?) millions of dollars advertising Steve Jobs. Peter Thiel was never on a billboard.

I don't intuitively think of "genius entrepreneurs" as a natural category...

That advertising (and similar hype) influences whom people think of as geniuses is a good point.