Yeah, it really depends on the kid. I think in general kids recognize the older Pokemon (particularly the ones from Gen 1), but don't really know about them as much. When they think Pokemon, sure, they think Pikachu, but aside from that, it's mostly Infernape, Dialga, Palkia, Giratina, Empoleon, etc. I'm sure that in a couple months I'll start seeing kids who really associate with the Gen V Pokemon, but I guess it hasn't been out long enough to see a lot of kids who have played only those games.
I was a lucky child, just about the right age for Pokemon coming out. My first memories are of watching Pokemon in England (in fact, I vividly remember the episode in which Ash battles Sabrina among others) when I was 3 or 4, so it's pretty much been a part of my life for as long as I can remember. I tend to know the Kanto Pokemon better than most (and to an extent Sinnoh - the games where I really started to get into team-building and such- and some Johto; Hoenn I'm a little rusty on).
I think it really depends on the child's exposure to the game - when they started playing, whether it was TCG or Video Games, and what was out at the time.
God, this really makes me want to pull out my Blue and play through it.