The division of RPG history into four generations, and even the term 'generations' itself, is somewhat contriversial. I personally disagree with it, as in fairness, the 'second generation' games consist of two very different sorts of games, and the 'third generation' games are consistant only if you narrowly define what games people were playing at the time. I also think that people who talk in terms of 'generations' tend to see it as a progression to increasingly advanced and more sophisticated forms. While there is some merit in that, in terms of game play, some of the more 'advanced' games technically turn out to provide generally inferior gameplay to earlier ones - which is why the early ones stick around.
I've seen two or three different descriptions of what even consitute '1st' and '2nd' generation, so I'm not even sure we can get agreement on an answer. Your answer in particular gives a progression that I don't think stands up very well, as what I would call a 'third generation' game (GURPS, Hero, Rolemaster) typically was very rules heavy, and the
'second generation' games take radically different approaches to the rules compared to D&D. (In fact, I would define the second generation of games primarily by the fact that they are all in some form, a responce to a percieved limitations of D&D.) Some of them are rules heavier ('C&S') and some of them are 'rules lite' (T&T).
Anyway, so here is my take.
0th Generation: 'Little Wars', parlor games, wargaming
1st Generation: D&D, TSR's other early specific genera games, other early genera games, and anything which is essentially an imitation of D&D initially, for example Gamma World's 1st edition.
2nd Generation: Games which in D&D's wake, that are specifically designed to address some percieved shortcoming in the D&D game system ('not realistic enough', 'not enough simulation', 'not enough customization' or conversely 'too arcane', 'too much dice rolling', 'not enough oppurtunity for story telling').
3rd Generation: A game which has been influenced by the lessons learned from the failures of the second generation. In particular, games influenced more by the design of RuneQuest than of D&D, and games which introduce rules intended to handle situations generally as a class of event rather than each specific situation with an individual rules. Following the 2nd generation trend, some of these are very rules heavy (Harn, Hero, GURPS, Rolemaster) and some of these are very rules lite (Paranoia, Toon).
4th generation: Games designed based on lessons learned from the 3rd Generation games, typically 'rules moderate' games which avoid complex simulationism in favor of faster gameplay and which avoid too much rules lite in favor of reducing the burden on DM judgement. (Also, rules lite proves to be an economically unsustainable trap, in that you can't sustain it with further sales). Often can be played consensually with little or no rules moderation (ei, no gamemaster). Sometimes involves different methods of arbitrating player conflict than dices.
5th generation: I would suggest that there is an emerging 5th generation of games which are influenced by what has been learned adapting RPGs to computers. In particular, these games are taking cue's from games like Fallout, Diablo, and WoW.
But, I'm not sure that 'generations' are the best description anyway, as D&D was arguably a 1st generation game right up until 3rd edition, when it hoped onto the 4th generation by way of design marriage. Also, you see some third generation games like 'GURPS' coming out before some second generation games, and then becoming a design trend. Also, you got to think that some of this isn't improvement, but rather just a fad - sort of like the 'ages' in comic books. Dark Age isn't necessarily better than Silver Age, it's just different.