i bought my sega genesis lot last year off a guy i believe was 25 or 26 and refuses to play anything newer then PS1.

I think some people its nostalgia
Some people its as said before that abstract feel that seems to have kinda been left behind due to games being made for realism
and some people its the simplicity of retro games.
You don't need to push a billion buttons and memorize a million commands and such. Just a simple tap of the A Button and your in heaven
and some people specially the younger generation that actually didn't grow up with a 16bit console or whatever. They wanna experience the stuff us older gamers experienced when we were growing up.

Its kinda like a mid 20s kid buying a 57 chevy belair.
Grandpa rants and raves how he had one when he was a young gun and use to take grandma out into town with it.
Kid wants to experience what grandpa experienced in a sense by buying that same car.