I think the latest generation of gaming has changed things greatly. Because gamer doesn't actually mean one group of people anymore. With the invention of Wii most families that have lots of kids have one, because it involves everyone including the grandparents.
I mean in games in general the list is endless on the different genre's and every genre has their elite stigmas of what they believe the vast majority of the people who play that genre are. I mean honestly how many people have ever heard of Jocks playing JRPG's? No Jocks totally play Madden and FPS's whether or not it's the truth.
I think the main categories we have right now are
Casual Gamers-Mothers, Children, people who play but don't really care
Noobs- Usually people who take the quickest cheapest method of killing someone
Hardcore- People who spend on average 72 hours of gameplay
Bro's- Generally associated with such games as Halo, Call of Duty, and Madden
Recluses- These are the normal sterotypes for WoW, Guild Wars, and Star Wars Galaxies
Nerds- in my experience are the people who are associated with RPG's. Persona, Final Fantasy, Zelda
Retro- People who play any system but the modern ones
And PC elitists- Those gamers who will never so much as pick up a controller so long as their mouse functions correctly.
(Not saying these are truths but generally these are the stereotypes associated with the genre of game out there)