Nice episode. A lot of thoughts and nostalgia.
Well I agree with a lot of things said by Rob, there are very few old games that has special mechanisms and styles that you will make you grab them and play them again and again (not because of nostalgia), most other games had been redone and improved upon them (whether it is sequel game or similar games done by different developers).
The example of Rise of Nations is good one, even if it is a generic RTS as play style, but it is one of the few that has this amazing balance and it is abstract of all historic period flavors, I gotta say there were other games tried to achieve the same like empire earth series and Empires: dawn of modern world, but RON had distinguishable balance, UI and overall aesthetic. The thing is after 2005 there was no attempt by any developers to make something similar to RON, and that is why in my opinion such a game will be played over and over.
I want to add about total war games, I see it evolving overall, and to be honest I dont see any right justification of the old ones to be superior, as much as I loved M2TW and had most fun playing it, I revisited it recently and there many annoying things in the campaign mechanism, buildings, UI, and the AI.
For games that have a really superior predecessor, I cant think of much, Stronghold games come to my mind.