I bought my own red box of basic D&D out of a Sears and Roebuck mail-order catalogue back around 1984. I also played Gamma World and TMNT back in that day too.
I never owned 1st ed. AD&D, but I played it. By this time, I was on to other games, mostly GURPS. For me, the switch to 2nd ed. was more of just a blip on the radar screen than anything earthshattering. By the time I was 22, I had also gotten into Games Workshop-style wargames (see, DND is a portal game for the wargame hobby!).
For me, there is no real nostalgia for 2nd ed., I won't claim that WotC stole my proposed fixes for the game, but we thought on the same lines (my suggestion for splitting classes was that humans should multiclass and demi humans should dual class, with level limits for demis and the humans' rep for being fast learners, it made more sense that way.)
I came back to the fold with 3rd ed. more with the idea that I could live with the new flexible system and use it to attract those who didn't have an inclination to learn a new game system. (I had gritted my teeth through TSR's imaginative settings like Dark Sun, Birthright and Planescape because the core books wasted a lot of page count trying to make a square peg of rules fit into a well-rounded world.)
So I voted for 2nd generation since I remember the early 1980s, which were curiously left out of the poll. Btw, I wouldn't consider TSR's playtesting phase of 2nd ed, to be part of the poll. You are asking the general public what generation they are, so you should stick to acutal product release dates since this is when the general public got to play.